valve; breadth more than double its length; hingeline straight, as wide as the shell; breadth 4 inches; length 1 inches.

This species belongs to the fusiform group of Spirifera, such as Sp. convoluta Phillips: it closely resembles in the straightness of the hinge-line and general form the Delthyris mucronata, Conrad, An. Rep. 1841, which has 20 serrated ribs on each side, and also the Sp. Lyellii of Verneuil; in the latter species the dorsal valve is much more gibbose than the ventral, and the smooth sinus is divided by a slight rib; in our species both valves are nearly equally convex, and the dorsal sinus has three distinct ribs. In the cast the lateral ribs are only observable near the margin, and the central muscular impression in the dorsal valve is very prominent and nearly orbicular. Locality.—Eagle Hawk Neck (Van Diemen's Land).

Spirifer Stokesii. (Pl. XV. fig. 1. 1 a.)

Syn. Trigonotreta Stokesii. (König, Icon. Foss. f. 70.) Sp. trapezoidalis, G. Sow. in Darwin, l. c. p. 159.

Shell globose, transversely obovate; mesial furrow broad, distinct, extending to the beak, with three slightly elevated ridges; lateral ribs four or five on each side, large, and rather rounded; beaks prominent, much incurved; hinge line as wide as the shell.

This is a very rough-looking species, in consequence of the paucity and size of the lateral ribs, which are sometimes subdivided into three, the central one being still prominent.

Locality. -Mount Dromedary (Van Diemen's Land). In limestone.

This species is very distinct from the Spirifer

trapezoidalis (Cyrtia Dalman), so that the specific name given to this species by Mr. König must consequently be adopted.

Productus brachytherus. (Pl. XIV. fig. 4, a, b, c.) Syn. Productus brachytherus, G. Sow. in Darwin, Volc. Isl. p. 158.

Trapeziform, very convex, with rather square sides, nearly smooth, spinose; base of the spines much elongated or decurrent; hinge-line straight, nearly the width of the shell; front slightly depressed.

This is rather a curious species of Productus; the surface of the shell has a silky aspect, and the base of the spines form long channels within the substance of the shell; the hinge-line is rather short, a character which, however, varies according to the age of the individual.

Locality.-Illawara, Raymond Terrace (New South Wales); Eastern Marshes, Mount Wellington, &c. (Van Diemen's Land).

Productus subquadratus.

Somewhat quadrate, gibbose, surface marked with irregular, coarse, longitudinal ribs, bearing bluntish spines; sides flattened; front produced; mesial furrow broad and distinct; hinge-line as wide as the shell; width 3 inches, height 2 inches.

This shell somewhat resembles P. antiquatus, but the mesial furrow is very defined; and there are no traces of the concentric undulations which cover the rostral portion of that species.

Locality.

Mount Dromedary and Mount Wel

lington (Van Diemen's Land).

There are one or two other species of Productus in too imperfect a state to be defined specifically.

GASTEROPODA.

Littorina filosa. (Pl. XVIII. fig. 4.) J. Sow. in Mitchell's Australia, Pl. II. fig. 5.

Shell turreted, acute, formed of six convex volutions, transversely marked by six rather acute and slender ribs, forming sulci between them; mouth

ovate.

This shell is figured in Sir T. Mitchell's Australia, p. 15., under the above name, which I have thought advisable to retain, as it would be difficult to decide the genus to which it otherwise belongs, from the imperfect state of preservation of the mouth in all the specimens hitherto examined.

This species so closely agrees in general form and size with the Loxonema sulcatula, M'Coy, that I should find considerable difficulty in distinguishing them. Mr. M'Coy mentions that his species is girt with about ten equal spiral sulcations; in the New Holland specimens these vary from six to eight. I should hesitate in placing either species under Loxonema, as the aperture appears to differ from the shells usually assigned to that genus, and the whorls are furnished with spiral ridges instead of the oblique arched striæ of Loxonema.

Locality. Booral (New South Wales).

Turritella tricincta. (Pl. XVIII. fig. 3.)

Shell elongate, composed of seven slightly flattened 'volutions, each spirally striated with three granular lines, the central one rather more prominent than the others; suture distinct; length half an inch.

This is an exceedingly small species, and resembles generally the characters given of T. acicula Phillips. Locality. Booral (New South Wales).

PLATYSCHISMA. (M'Coy.)

P. oculus. (Pl. XVIII. fig. 1.)

Syn. Trochus oculus, J. Sow. in Mitchell's Australia, Pl. II. fig. 3, 4.

Shell suborbicular; spire short, conical, and obtuse, with four gradually increasing volutions, the last one having an obtusely carinated edge; aperture subtrigonal; umbilicus deep; base somewhat convex.

This species so closely agrees in nearly all its characters with the P. cirroides M'Coy, that I feel some hesitation in considering them as distinct; the figures and description of that author answer tolerably well for our species, which is however rather more depressed; and the well-preserved conditions of the specimens exhibit the pearly lustre of the original shell, which appears to have been rather thick, and furnished with a distinct and deep umbilicus.

Locality. Harper's Hill (New South Wales). Abundant.

P. rotundatum. (Pl. XVIII. fig. 2)

Shell nearly orbicular, obtusely conical; volutions four, gradually increasing, and distinctly rounded; base convex; aperture suborbicular.

This species agrees in nearly all the important characters with the last, of which it might be considered merely a variety; the volutions are more distinctly rounded, and the inner part of the outer lip appears to have been periodically thickened, leaving deep sulca

tions in the cast of this shell; the shallow sinus in the outer lip is not well defined in this species; and from the thick and pearly shell, the distinct umbilicus and undefined suture, it might have been associated with Trochiscus G. Sow. In that genus, however, the shallow sinus appears to be wanting.

Locality. Harper's Hill (New South Wales). Abundant.

Pleurotomaria Strzeleckiana. (Pl. XVIII. fig. 5.)

Shell subturreted, umbilicate, formed of five rather rounded volutions, separated by a distinct suture; an obtuse keel, defined in the cast by two slight sulcations, divides the volutions into two nearly equal parts, of which the superior is rather the smaller; base and columella rounded; aperture longitudinal. The lines of growth turn rather abruptly backwards from the suture to the keel, and afterwards gradually curve towards the umbilicus. Right lip somewhat angular, and furnished with a deep fissure corresponding to the external keel.

This shell presents the general contour of Pleur. vittata Phillips, Geol. York. t. 15. f. 24.; but is well distinguished by having an obtuse keel instead of the broad and flat band of that species; it also resembles in size and form the P. tornatilis Phil., as figured by De Koninck, in his work on the carboniferous fossils of Belgium. This appears to be an abundant species, and occurs both at Illawara and Glendon, New South Wales.

I have dedicated this species to the author of the present work, to whose indefatigable industry we are indebted for a more intimate knowledge of the physical structure of the Australian continent.