450 MANUAL OF THE MOLLUSCA. 
chamber from 2 to 7 diameters; specimens measuring a yard 
across may be seen on the cavernous shores of the islets near 
Rochelle.* (Pratt.) 
Fossil, 6 species. Neocomian—Lower Chalk. France, Portugal, 
Texas. 
oN 
x 
i\ 
Yy Ye 
RYU +S 
h> 
Fig. 249.C. Aguillonz, left valve Fig. 250.C. adversa (after D’Orb.). 
a, a, position of adductors; /, ligament; uw, umbonal cavity; ¢, tooth of fixed valve, 
broken off and remaining in its socket ; c, original point of attachment, 
Caprina, 0. D’Orbigny. 
Etymology, caprina, pertaining to a goat. 
Synonym, Plagioptychus, Matheron. 
Type, OC. Aguilloni, C. D’Orbigny. Lower Chalk, Tyrol 
(= C. Partschii, Hauer). 
Shell with dissimilar valves, cartilage internal; fixed valve 
conical, marked only by lines of growth and a ligamental 
groove; hinge-margin with several deep cartilage-pits ; and one 
large and prominent tooth on the posterior side; free valve 
oblique or spiral, thick, perforated by one or more rows of 
flattened canals, radiating from the umbo and opening around 
the inner margin; anterior tooth supported by a plate which 
divides the umbonal cayity lengthwise, posterior tooth obscure ; 
hinge-margin much thickened, grooved for the cartilage. 
In C. adversa (Fig. 250) the free valve is (0) sinistrally spiral ; 
its cayity is partitioned off by numerous septa, and divided 
longitudinally by the dental plate. When young it is attached 
by the apex of the straight valve (c), but afterwards becomes 
detached, as the large specimens are found imbedded with the 
spire downwards. (Saemann.) The lower valve of C. Coquandiana 
is sub-spiral. 
* These singular fossils were called ichthyosarcolites by Desmarest, from their 
resemblance to the flaky muscles of fishes. 
