688 APPENDIX I. 
20. Protapomya (Homomya) curvara [2] (J. Morris,) Dana.—Plate 8, fig. 2, a, 6, 
different views, natural size. 
District of Illawarra, at Wollongong Point. 
Morris’s figure, in Strzelecki’s New South Wales, represents a proportionally broader 
shell, but has the general habit of the specimen in our collections, except that the plica- 
lions seem, in his figure, to pass into striae, which is not the case as observed by the 
writer. The right valve is a little the larger ; and the radiations, plications and character 
of the surface, as well as the gaping posterior, are similar to the same in the audaz. 
2 . 7 60 ° jel 50 
Length 47 inch ; height ,%°, L.; thickness ,5% L. 
Allorisma curvatum, J. Morris, op. cit., p. 270, pl. x, fig. 1. 
Nore.—The above two species may belong to the genus Al/orisma of King: but it is 
dificult to detect any sufficient characters for separating them from Pholadomya (or 
Agassiz’s Homomya,) provided the palleal impression is not entire. The specimens are 
external casts, 
21. Astarrr Gemma (Dana).—Small. A little oblong, nearly mequilateral. Lateral 
surface regularly convex ; neatly marked with numerous fine deep sulci. Valves crenu- 
late within. Palleal impression faint; impression of larger anterior muscle somewhat 
excavate, of smaller oblong, of posterior muscle faint—lLength 3 inch; height 835 L. ; 
thickness #43, L.; anterior part ;’; of the whole length ; apical angle 140°.—Plate 3, fig. 
4, view of cast, natural size; a, cast of exterior surface of an imperfect valve ; 6, enlarged 
drawing, showing cast of hinge. 
Wollongong Point, District of Illawarra. 
In this cast, the impression of two divergent teeth is finely preserved. The palleal 
impression, though faint, is distinctly entire. The fine strive, or ridges of the surface, 
number four or five to a line in breadth, and the crenulations, near the margin of the 
valves, are about four to a line. The cast of the interior has a smooth surface. 
Astarte gemma, Exped. Foss., Amer. Jour. Sci., il. Ser., iv. 154. 
Genus ASTARTILA (Dana).—KEquivalve, inequilateral, transverse, throughout con- 
vex, externally marked with concentric striz. Ligament external, extending to the pos- 
terior extremity of the cardinal area; umbos of moderate size. Palleal impression 
entire. Muscles two anteriorly and one posteriorly; the smaller interior under the 
beaks, and directed inward ; the larger broad, subelliptical, or suborbicular ; the posterior 
also broad. Valves having the interior surface, from the umbos obliquely downward, 
flattened, or a little raised, [producing a flattened or excavate area on the lateral surface 
cf a cast.] 
This genus has many of the characters belonging to Astarte, and perhaps should be 
considered as only a subgenus in that group. ‘The form is more transverse; the beaks 
are more to one side, the anterior portion of the shell varying from 1 to 2 of the whole 
length; and the ligament is much longer. Besides, the cast has the beak obliquely trun- 
cate at apex, and is flattened laterally on the side of the beak. ‘There is usually one or 
two folds or lines extending from behind the beak obliquely downward, so as to pass 
