68 
isocardioides ,) a minute fossil in many respects closely re- 
lated to it, but said by Lea to be destitute of teeth : as he 
says nothing about the ligament, but mentions the close ap- 
proach of its general characters to those of Isocardia , it is 
probable that the ligament winds up under the beaks as in 
that genus, and so Philippi describes it in his H. acuticos- 
tatus. The general form of Lea’s type of Hippagus is very 
different, but the resemblance of the hinge is great, and 
he says the edge of the shell is toothed; upon the whole 
therefore we adopt his genus for this shell, but with doubt, 
and have made some additions to his Gen. Char, with a 
view to its including both shells. The name Ve rticordia 
was hastily adopted on early impressions of the plate from 
Mr. Wood’s manuscript, but is objectionable, having been 
long ago applied to a plant. 
HIPPAGUS ? cardiiformis. 
TAB. DCXXXIX. 
Spec. Char. Convex, orbicular, costated ; costae 
15or 16 prominent, obtuse, rugoselysquamose, 
projecting beyond the edge, furrows finely 
granulated ; umbones incurved. 
Syn. Cryptodon Verticordia, S. V. Wood, Catal. 
Ann . and Mag. Nat. Hist. v. vi. 247. 
An orbicular shell, rendered beautiful by the curvature of 
its ribs and almost pectinated margin ; internally the ribs 
are indicated by slight furrows. It is produced by the co- 
ralline Crag of Sutton ; about twenty individuals, single 
valves, have been found. 
Hippagus acuticostatus (Phil. Enurn. v. ii. 41. tab. 14. 
f. 19.) is distinguished by sharp lamellar ribs, of which 
there are only 13, not 15 or 16 which our shell has, and 
by the corresponding furrows within being confined almost 
to the margin, neither do they project so far beyond the 
edge of the shell ; in size and other respects the two shells 
hardly differ. 
