18 © 
PALAEONTOLOGY OF NEW-YORK. 
Strophodonta varistriata. 
Plate YIII. Fig. 1 - 16 ; and Plate XYI. Fig. 1-8. 
Strophomena varistriata : Conrad, Jour. Acad. Nat. Sci. Philadelphia, Vol. iii, pa. 255, pi. 14, f. 6. 
S. redilateris : Loc. citata, pa. 255, pi. 14, f. 7. 
S. impressa : Loc. citata, pa. 255. 
Leptcena indenta [ ? ] : Conrad, Ann. Rep. on the Palaeontology of New-York, 1838, p. 117. 
Shell semioval, varying in form from length and width equal, to length 
greater or less than the width : hinge line equal to or greater than the 
width of the shell below; extremities rounded or salient. Dorsal valve 
flat, or more or less concave according to the convexity of the ventral 
valve, but not conforming entirely to the curvature of the latter. Ventral 
valve varying from slightly convex to gibbous, and sometimes abruptly 
arching towards the front : umbonial region more or less prominent; 
beak usually a little elevated. Area narrow, almost linear. Foramen 
linear or none*. 
Surface often finely and evenly marked with straight or slightly undu¬ 
lating strife ; more often with prominent sharp striae at more or less 
equal distances from each other, and the intermediate spaces by minute 
equal strife ; and again in other specimens by alternating larger and 
smaller strife, of which there are frequently three regular gradations 
in size. Radiating strife crossed by fine concentric elevated lines, and 
often by undulations or indentations which are more conspicuous on 
those shells where the strife are in fascicles of finer between stronger 
ones. Vascular impressions of the ventral valve circumscribed by la¬ 
mellae, more or less distinctly flabellate : impressions of adductor 
muscles elongate-oval. 
* The representations of the foramen on Plate vm are erroneous, there being no triangular opening of 
the kind; this feature proving, on careful examination in numerous individuals, to be due to fracture, as is 
common in this part of other species of the genus, and particularly in the separated valves of the typical 
species. 
