692 APPENDIX I. 
form of the cast (in a transverse section) is cuneate, it thinning towards the lower margin, 
which is thin and acute, and slightly arcuate in outline, or nearly straight, instead of ex- 
cavate, like the following species. The cast much resembles the Solemya primeva of 
Verneuil (Pal. of Russia, pl. 19, fig. 5). The form of the shell approaches that of the 
Actinodonta cuneata of Phillips, (Mem. Geol. Surv. Brit. 1848, ii, 366.) 
Cardinia recta, Exped. Foss., Amer. Jour. Sci., ii. Ser., iv. 156. 
30. Carpinia ? cunEatTa (Dana).—Very inequilateral, length very nearly twice the 
height. Narrowing considerably behind. Superior margin strongly arcuate; infe- 
rior straight at middle, or slightly excavate ; anterior obliquely truncate. Exterior sur- 
face with concentric striz of growth, and without radiations ; laterally somewhat com- 
pressed. Larger anterior muscular impression deeply excavate ; posterior faint ; cardinal 
area of cast long linear, and bounded by a prominent carina, extending quite to the pos- 
terior margin.—Length 17 inches; height ~?5 L.; thickness ,°3, L. Apical angle of cast 
110°.—Plate 4, fig. 6, 6 a, 6, different internal casts, natural size ; c,d, other views of a; 
e, front view of 0. 
Wollongong Point, District of Illawarra, 
This species is proportionally higher, and narrows more rapidly behind than the vecta, 
and, moreover, it is much thicker, and the cardinal area in the cast has not the prominent 
inner margin in that species, while the outer is quite prominent. Along the back, the 
shell is nearly truncate, and wide, (about 7 inch,) and the surface (as appears from a 
cast) is marked with fine lines, extending backward from either side of the ligament, 
slightly divergent. The sides of the cast are strongly compressed, or a little con- 
cave, while the sides of the beak are also flattened. 
Cardinia cuneata, Exped. Foss., Amer. Jour. Sci., il. Ser., iv. 156. July, 1847. 
Cardinia exis, M’Coy, Ann. & Mag. Nat. Hist., xx. 302, Nov. 1847, pl. 15, fig. 1. 
31. Carprnra ? costara (J. Morris), Dana.—This species, described and figured by 
Morris, has a Jength tree times its breadth, and fowr times its thickness. The sides are 
compressed just posterior to middle. The lower margin is straight, or slightly excavate ; 
the dorsal is very nearly straight, (slightly convex,) and parallel nearly with the lower ; 
the posterior is arcuate. ‘The lateral surface is unevenly concentric striate or rugose, 
and it is radiate or radiately costate, mostly posterior to a line from the anterior part 
of the beak to the middle of the lower margin. The posterior muscular impression is 
large, broad, elliptical, and a little excavate; the larger anterior is deeply excavate ; and 
above it, in the cast, there is an oblique concave surface, from the anterior part of which, 
obliquely downward and backward, there is, in the cast, a broad, flattened area ; and pos- 
terior to this, there are some radiations. The cardinal area of the cast is long, narrow 
linear and concave. The surface adjoining is broadly rounded instead of carinate.— 
Length 43 inches; height 335 L.; thickness {%° L.; apical angle about 130°.—Plate 4, 
fig. 8 a, b, views, natural size ; c, vertical section. 
Orthonota ? costata, J. Morris, in Strzelecki’s New South Wales. 273, pl. xi., figures 1, 2. Mr. 
James Hall, of the New York State Geological Survey, agrees with me that the above species 
cannot belong with the Orthonota of Conrad. 
Genus PACHYDOMUS.—This genus, first described by Mr. Sowerby under the 
name Megadesmus, and afterwards designated Pachydomus by Morris, (as the previous 
