ckagin.] DESCRIPTIONS OF SPECIES. 67 
Eriphyla especially seems to be largely represented among the fossil Astarte, 
as recorded at the present time, and probably all the species which have an 
indication of a posterior pallial sinus belong to the former genus. They can 
scarcely be referred to Astarte, for the single anal opening which the animal 
of this last possesses lies behind the posterior muscular scar, but not below it. 
'where the formation of a sinus, if present, must be due to the development of 
muscles supporting a branchial siphon, or at least a special branchial opening. 
Neither of these are, however, present in Astarte. 
But so gradual is the transition from none to a well-marked pallial 
fsinus that it seems impossible in practice to distinguish Eriphyla from 
jAstarte clearly by this criterion. 
Astarte posticalva sp. n. 
PL XI, tigs. 5, 6. 
Shell small, thin, triangular-ovate, of intermediate convexity; 
)eaks rather prominent and pointed, directed somewhat forward, 
interiorly excavated, placed near and usually back of the limit of the 
[interior third; posterior slope a little flattened; anterior three- 
fourths (to four-fifths) of shell ornamented with numerous linear 
oncentric costellse, which are separated in strong relief by deep striae 
ibout half as wide as themselves; the flattened posterior fourth or 
ifth forming a sort of area which is plain, or marked with ordinary 
;rowth lines only, and is separated from the preareal surface by a 
ery obtuse or rounded radial angulation which is not of itself a dis- 
crete and salient feature, but consists merely of the rather abruptly 
;urved transition from the outer to the flattened posterior slope of 
;he shell. The costella? are deflected at their posterior ends, vanishi- 
ng rather rapidly, but not abruptly, as they approach the plain area. 
Measurements. — Height, 13 mm.; length, 15 mm.; breadth, 10 mm. 
K. valve of another specimen has a height of about 1-t mm. and a 
ength of 17 mm. 
Recurrence. — Not infrequent H miles east of Malone station. 
Twenty-one specimens were collected. 
Astarte? fsodontoides sp. n. 
PL XI. figs. 8, 9. 
Shell small, gibbous, inequilateral, oblong-ovate, the dorsal line 
ently declivous and slightly convex back of the beaks and very 
eebly excavated in front of them; base nearly straight; anterior 
ide rounded; posterior side obliquely truncated; beaks low, in con 
act, situated near the anterior third, an obtuse umbonal ridge or 
lflation extending from their summits to the postero-ventral margin, 
nd the greatest breadth of the shell being, by reason of such infla- 
