which, provisionally and for the purpose of registration, I assigned the name "granicone," suggested by their shape and surface.

All were conical, with a comparatively smooth base (Fig. 4, b); the rest of the outer surface was of a denser and smoother texture, but beset with granules of about a millimetre in diameter, more or less. The largest of these "granicones" are the subjects of Figs. 1, 2, and 3; the smallest were rather more than half that size. The variations of shape were in the degrees of obliquity of the base, the extreme of deviation from a right angle to the cone's axis being shown in Fig. 4. The margin of the base was formed, in some, by a single series of granules, like a circle of beads, as in Fig. 5, from which the apex of the cone was broken away.

Conceiving these bodies to be dermal bones or appendages, their conical shape suggested first a comparison with those of certain rays and sharks, but the osteo-dentine and ganoine shown in microscopical sections, and the disposition of the canaliculi ramifying from the central cavity, at once distinguish the structure of such piscine dermal cones and spines from that shown in similar sections of the granicones.

I may add, also, that the geological deposit containing these fossils is a fresh-water one, and that no evidence of Sturionidæ or other fishes with ganoid plates, habitually or temporarily frequenting rivers or lakes, has been met with in the portions of matrix showing the fossil bodies in question.

Bones and teeth of various Reptilia are, however, abundant. They have afforded materials for a monograph on certain new and small forms of Crocodilia; but the associated osseous scutes, or dermal bones referable to this order of Reptilia are unmistakable. On the hypothesis of the "granicones" being similar parts of some member of the same cold-blooded air-breathing class, there were several extinct genera of Lacertilia, represented by associated fossil bones and teeth, to one of which, it seemed probable, the bodies in question might have belonged.

I may remark that in certain Dinosaurs (Hylæosaurus, Scelidosaurus, e. g.), some of the dermal scutes with flat or with oblique bases of attachment, rise thence in a pyramidal form. But these much exceed in size the largest of the "granicones." There was no trace, moreover, of any species of either of the above extinct Wealden or Liassic genera in the Becklesian Collection.

The associated Lacertian fossils which, by their number and

* "Tubes de dentine" of Prof. Hannover, who, in his excellent memoir 'Sur la Structure et le Developpement des Ecailles et des Épines chez les Poissons cartilagineux,' thus describes their course in the dermal scales along the mid-line of the back of the sting-ray (Trygon):-" Du réseau sortent les tubes de dentine, qui rayonnent de tous les côtés dans la partie libre et pyramidale de l'écaille," p. 3. See also Quekett, Histological Catalogue, Mus. Coll. of Surgeons,' 4to, vol. ii. 1855, pp. 86, 87.

size, best agreed with the granicones, on the hypothesis of these being "dermal bones" of such, were the teeth (Figs. 9 and 10), and bones (Fig. 8) of the extinct species which I have called Nuthetes destructor.*

Amongst the existing forms of Lizards the dermal armour of the Australian species Moloch horridus is that which most resembles the bodies in question, except that the surface of the cone is smooth and corneous, the hard, horny cone being hollow, and sheathed upon a conical process of dense dermal tissue. I have not detected a trace of ossification in this tissue of the existing lizard.

The resemblance, however, of its texture, as exposed by thin slices, with a section of the bony body of a "granicone," such as is shown under a moderately magnified power in Fig. 7, Plate XII., was suggestively close. Decussating bands of fibrous tissue, closely matted, in the body of the dermal cone of Moloch, wanted only the addition of osseous matter to repeat the texture shown in Fig. 7.

I have already referred to the characteristic microscopical structures of the conical scutes and spines of the Thornback-rays, Trygons, and other Placoids of Agassiz. In Quekett's excellent and useful work the osseous tissue of the endo-skeleton only of the class Reptilia is described and illustrated. The scutes, spines, and scales of the Lacertilia, indeed, so far as I have yet observed, with the exception of the long spines supporting the crest of the Basilisk, are horny, and supported by dense though unossified corium. But in the existing Crocodilia, especially in the dorsal region, the larger scutes have an osseous basis, coated by a thin horny or epithelial layer.

The application of the histological characters of the fossil dermal scutes associated in the same slab of matrix with the bones and teeth of the small Purbeck Crocodile (Theriosuchus pusillus, Ow.) induced me to resume a long-abandoned line of research, and to submit the results to the Society, in the establishment of which I had the pleasure to co-operate at a period when a great proportion of my anatomical researches was aided by the microscope.

In Plate XIII. a dorsal scute of the Crocodile in question is outlined of the natural size in Fig. 1, and the mode of overlapping is indicated by the dotted line in a contiguous scute, twice the natural size, in Fig. 2. The scutes in the present extinct genus have the same peg-and-groove joints as in the larger Purbeck genus Goniopholis, but the dentition of this crocodile is generically distinct from that of the diminutive Theriosuchus.

*Monograph on the Fossil Lacertian Reptiles of the Purbeck Limestones,' in the volume of the Palæontographical Society, issued 1860, 4to, p. 31; and 'Quarterly Journal of the Geological Society,' 1854, p. 129.

Op. cit., pp. 108-134, plates viii. and ix.

The section of the scute (Fig. 3) exposes the large and irregular sinuses from which the Haversian canals are continued, and the numerous bone-cells or "lacunæ." The structure of the latter, as seen in transverse sections, is shown by the higher magnifying power, 500, in Fig. 4. They are notable for the great number of their canaliculi, and their correspondence with those of the osseous tissue of the femur of the Crocodile is close. The dermal bone is chiefly distinguished by the greater proportion of the unossified part, indicated by the wider sinuses which are filled in the fossil by the opaque matrix.

A section of a granicone (Plate XII., Fig. 10) showing some of the "lacunæ" in transverse section; others longitudinally divided, differs from the crocodilian scute in the fewer sinuses and more numerous Haversian canals, the direction of which is followed by the long diameters of the lacunæ.

The section of the osseous tissue of the femur of a Monitor Lizard, figured by Quekett (plate ix., fig. 30), shows the same diversity of the "lay" of the lacunæ, some being divided transversely, others obliquely or longitudinally, as in the section of the granicone herewith submitted to the Society, and part of which is figured in Plate XII., Fig 10.

In both dimensions, in size, shape, and number of canaliculi, the lacunæ of the granicone most nearly resemble those of the Lacertians, as described and figured in Quekett's Histological Catalogue' (vol. ii. p. 122, plate ix., figs. 17, 30, 32). I therefore_conclude that the granicones are dermal scutes, that they are Lacertian, and, as far as contiguity and association indicate, have formed part of the external armour of the large extinct Purbeck Lacertian, Nuthetes destructor.

If my determination prove correct, this species must have presented the same formidable and singular character of dermal defence as does the recent Australian lizard already alluded to, and which has thence received the name of Moloch horridus. The chief distinction is the ossification of the horn-like scutes in the old secondary genus, whereby they have come down to us in the fossil state.

It is not without interest to note that the mammalian fossils associated and contemporaneous with the Nuthetes are marsupial, and that wherever a family or generic relationship can be determined between them and still existing or recently extinct species, such species, like Moloch horridus, are Australian.

Quekett, op. cit., pl. ix. fig. 7.

II.-On some New Genera and Species of Diatomacex. By M. P. PETIT. Translated by F. Kitton, Hon. F.R.M.S., by the kind permission of the Author.

(Taken as read before the ROYAL MICROSCOPICAL SOCIETY, June 5, 1878.) PLATES XIV. AND XV.

IN the 'Fond de la Mer' M. P. Petit has given a list of Diatomaceæ collected by the expedition sent by the French Government to Campbell Island,* in the year 1874, for the purpose of observing the transit of Venus. Dr. Filhol, one of the gentlemen appointed by the Government, after leaving the expedition, travelled alone in New Zealand, and the forms obtained by him are also inIcluded in M. Petit's list.

DESCRIPTION OF THE PLATES.

PLATE XIV.

FIG. 1.-Coccone is notata (P. Petit), n. sp.

9

2.

australis (P. Petit), n. sp.; a, frustule; b, inferior valve; c, superior do.

3.--Cocconeis Wright (O'M.), new form.

Crux (Ehr.).

5.-Campyloneis Grevilli (Grun.); a, frustule; b, one of the plates of the inferior valve; c, second plate of do.; d, superior valve.

6.-Rhaphoneis fasciolata (Greg.), n. var.

7.-Hyalodiscus maximus (P. Petit), n. sp. × 200 diameters; a, valve; b, f. v. of do.

16.-Stauroneis robusta (P. Petit), n. sp.; a, valve; b, frustule.
17.-Amphiprora rugosa (P. Petit), n. sp.
18.-Surirella Filholii (P. Petit), n. sp.

19. Trachysphenia australis (P. Petit), n. gen. and sp.

20.-Grammatophora marina (Kg.), n. var.

21.

24.

longissima (P. Petit), n. sp.

22.-Rhabdonema hamuliferum (Kitton), n. sp. 23.-Navicula Campbellii (P. Petit), n. sp.

quærnerensis (Grun.), var. dilatata (P. Petit).

25.-Auliscus stelliger (P. Petit), n. sp.

All the figures, excepting Fig. 7, are × 600 diameters.

* Campbell Island is in the South Pacific; lat. 52° 33' S., long. 169° 8' E. (London). It is of volcanic origin, 36 miles in circumference, and 1500 feet above the sea-level.

COCCONEIS.

1. C. notata (P. Petit). Valves ovate, median line sigmoid, central nodule dilated into a smooth band (pseudo-stauros) reaching the margin and terminated at one margin by a circular hyaline enlargement. Striæ transverse, very close, subradiant, and finely punctate, reaching median line. Length 26 μ 4, breadth 13 μ 6. Lyell's Bay. Pl. XIV., Fig. 1.

*

2. C. australis (P. Petit). Valves dissimilar, small suborbicular, the inferior (Fig. 2b) having a sigmoid line. Striæ longitudinal, close. The superior valve (Fig. 2c) smooth, but furnished with short distant marginal costa (closely resembling the canaliculi of the Surirella). Length 26 μ 4, breadth 24 μ 2. Lyell's Bay. Pl. XIV., Fig. 2.

3. Raphoneis fasciolata, var. australis (P. Petit). This form shows characters differing from the type. The rows of granules increase in length as they approach the centre, producing a very marked contraction in the smooth space occupying the centre of the valve. This variety is very variable in shape and size, its length varying between 28 μ 6 and 55 μ.

Lyell's Bay, where it is very abundant, but it does not occur in other localities. Pl. XIV., Fig. 6.

HYALODISCUS, Ehr.

(Cleve emend.: Diatoms from the Arctic Sea, p. 4.)

Note on the Genus.-M. Cleve has already verified the affinities. of all the discoid species with a central fracture or umbilicus. These he has correctly united in a single genus Hyalodiscus of Ehrenberg. We have moreover remarked, that in all the species placed in Podosira the zone is curved in an opposite direction to that which exists in P. Montagnei. In examining H. hormoides (P. hormoides, Ktz.) living, we have seen that the endochrome has nothing in common with that of the true Podosiræ; it is granular, as it is in the Melosire to which it belongs. The endochrome in H. hormoides forms a single plasmatic layer with four lobes, and always resembling in disposition the endochrome of Achnanthidium; it is only in contact with one side. These characters clearly indicate that H. hormoides ought to be classed with the Achnanthem if we follow the system of classification proposed in our list of diatoms,† and it is probable other species of the genus exhibit the same peculiarities if we had the opportunity of studying them.

4. H. maximus (P. Petit). Valves discoid, very large, central 0001 of a metre, 001 of an English inch = 25 μ 339.

* 1μ =

+ See M. M. J.,' vol. xviii. p. 10.

Eulenstein has previously published a species which he has named maximus. See Habirshaw's 'Catalogue of the Diatomaceæ.'