126 PALEOZOIC PALEONTOLOGY. 
SYNTROPHIA LATERALIS (Whitf.). 
Plate IV., Wigs. 14-15. 
1886. Triplesia lateralis Whitfield, Bull. Am. Mus. Nat. Hist., vol. 
I., p. 303, pl. 24, figs. 9-11. 
Description.—Shell subelliptical in outlne, hinge-line about two- 
thirds the greatest width, cardinal extremities broadly rounded. 
Pedicle valve moderately convex, most prominent on the umbo, 
slightly flattened toward the cardinal angles; beak rather blunt, pro- 
jecting beyond the cardinal margin, slightly incurved; mesial sinus 
broad, shallow and ill-defined, not reaching to the beak. On some ex- 
foliated specimens a dark line, representing the median septum, may 
be detected extending forward from the beak for several millimeters. 
Surface marked by fine, concentric lines of growth. Brachial valve 
not seen. 
The dimensions of an average specimen are: length, 7.5 mm.; 
width, 11 mm. 
Remarks.—None of the New Jersey specimens of this species are 
very perfectly preserved, and they differ in some minor respects from 
Whitfield’s illustrations of the types of the species from Fort Cassin, 
but there can scarcely be a doubt as to the identity of the shells from 
the two localities. The New Jersey specimens are proportionally a 
little longer than the original illustration of the species, and the 
mesial sinus of the pedicle valve is a little less angular, but these 
differences can scarcely be more than individual variations. The 
shell described as Syntrophia palmata by Cleland from Fort Hunter, 
New York, is also probably specifically identical with Whitfield’s 
species and the New Jersey specimens. 
