56 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
the lower portion of the anterior border is elliptically curved ; the base is nearly straight ; 
the inner borders of the valves are crenulated ; the surface has closely arranged, delicate, 
unequal, longitudinal striations, which are decussated upon the anterior side by others 
which radiate from the umbones, and when the outer layer of the test has been removed 
a series of strongly marked, radiating striations are exposed over the whole of the 
valve; both kinds of striations are also impressed more or less distinctly upon the 
nucleus. 
This delicately ornamented Cypricardia might at the first glance be mistaken for a 
depressed variety of Cypricardia cordiformis, Desh., a shell which in the young condition 
possesses great differences of figure ; it will be found, however, that Cypricardia caudata is 
more depressed, more trigonal, the anterior side more lengthened, and the posterior angle 
much less defined, so that the portion of the surface posterior to it is even somewhat 
convex ; but in Cypricardia cordiformis it is flattened or often slightly concave in some 
instances ; the entire absence of ornamentation, both upon the test and the nucleus, is 
another distinctive feature. The fine specimen figured has the area delicately preserved, 
and exhibits the ligament; the test is of moderate thickness, and the mner borders of 
the valves are crenulated ; an exposed portion of the nucleus has striations corresponding 
to those upon the inner layer of the test. 
Geological Position and Locality. 'Yhe Cornbrash of Northamptonshire ; also in the 
Forest Marble of Wiltshire, obtained by W. Walton, Esq. 
Isocarpia minima, Sow. Tab. XXXVI, figs, 1, 1 a. 
IsOCARDIA MINIMA, Sow. Min. Con., t. 295, fig. 1. 
_ — Phaltips. Geol. York., 1, t. 7, fig. 6. 
a a Morris. Catal., 1854, p. 204. 
— — ? Quenstedt. Der Jura, p. 443, pl. 60, fig. 17. 
Non Isocarpia mintma, Goldf. Pet., p. 211, t. 140, fig. 18. 
Testa crassa, levigata, tumida, umbonibus parvis submedianis incurvis, margine dorsali 
oblique-curvato, lunula excavata ; lateribus striis concentricis crebris equalibus, tenuissimis 
instructis. 
Shell thick, smooth, convex ; umbones small, somewhat oblique, and placed a little 
anterior to the middle of the valves; dorsal border curved obliquely ; lunule excavated ; 
the surface of the valves with very delicate, closely arranged, concentric striations. 
A smooth, short, rounded, and moderately convex shell, with rather small umbones, 
quite different from the casts figured by Goldfuss and attributed by him to this species, 
but which probably belong to the genus Cardium. 
The single figure given by Quenstedt is much more inflated, with larger umbones, 
