DEVONIAN FAUNAS. Zo 
MOLLUSCA. 
PHELECYPODA. 
RHOMBOPTERIA CLATHRATUS Nn. Sp. 
Plate XXXI., Figs. 16-18. 
Description.Shell inequivalvate, oblique, subrhomboidal in out- 
line, the anterior and posterior margins subparallel, the basal margin 
rounded. Huinge-line straight, produced anteriorly, as well as pos- 
teriorly from the beak, which is located anterior to the middle. Left 
valve strongly convex transversely across the umbonal ridge, scarcely 
auriculate in front, a shallow, indefinite sinus extending from the 
beak nearly vertically to the anterior margin. Surface marked by 
broad, concentric bands, which, on their lower margins and reaching 
for more than half their width, are crossed by two sets of fine striz, 
making an angle with each other. The right valve associated with 
this shell, and doubtless belonging to it, is nearly flat, with rounded, 
concentric wrinkles, not marked by the cross-lines of the left valve. 
A left valve somewhat larger than the average has a height, ob- 
liquely from the beak to the basal margin, of 22 mm.; its width, at 
right angles to this line, is 15 mm., and its convexity, 5 mm. 
Remarks.—This species is rather common in the uppermost beds of 
the Coeymans limestone near Hainesville. The left valves are by 
far the most common, but very few specimens of the right valve, and 
all of these small, having been observed. Many of the specimens are 
entirely exfoliated, so that only the concentric bands can be recog- 
nized, the finer cross-lined surface markings being wholly obliterated. 
On the casts the anterior sulcus, extending vertically downward from 
the beak, is far more conspicuous than when the shell is preserved, 
and consequently, also, the anterior auriculation of the shell. 
In general form and in surface markings this species resembles 
Rhombopteria mira Barr., from Bohemia, which has been made the 
type of the genus by Jackson,* but the anterior cardinal angle is more 
broadly rounded in the American shell and it is less auriculate an- 
teriorly. 
* Mem. Bost. Soc. Nat. Hist., vol. IV., No. 8, p. 380. 
