180 PERMIAN FOSSILS. 
CARDIOMORPHA MODIOLIFORMIS, King. Plate XIV, figs. 18, 19, 20, 2], 22, 23. 
PLEUROPHORUS MODIOLIFORMIs, King. De Verneuil, Bull. Soc. Geol. de France, 2™° série,- 
t. 1, p. 32, 1844. 
— — Geol. Russ., vol. i, p. 224, 1845. 
CARDIOMORPHA —— » King, Catalogue, p. 10, 1848. 
MyoconcHa — », Howse, Trans. T. N. F. C., vol. 1, p. 245, 1848. 
Diagnosis.—Modioliform: tumid diagonally in the umbonal region, and compressed 
towards the margins: measuring three quarters of an inch from the point of the 
umbones to the posterio-ventral margin: marked with rather distant lines radiating 
from the umbones posteriorly, the lines being raised in young individuals, and impressed 
in old ones. Umbones incurved. Lwunette heart-shaped. Corselet long, rather shallow, 
defined by a rather prominent ridge, which curves in both valves from the point of the 
umbone to the termination of the hinge. Axferior muscular impressions bounded pos- 
teriorly by a slightly elevated ridge. 
Cardiomorpha modioliformis, in its marginal outline, bears a resemblance to some 
varieties of Cardiomorpha Pallasi (Mytilus id.'), De Verneuil; but it is a shorter and a 
more tumid species ; and its umbones are more incurved: in the latter character, and 
in bemg diagonally tumid, it approximates to Cypricardia glabrata, Phillips,—a species, 
which, had it occurred in the Permian rocks instead of the Carboniferous, I might 
have considered identical with the present one. It has very much the aspect of a 
Modiola, particularly one variety, which is distinctly lobed in front (vide Pl. XIV, 
figs. 20, 23). Old specimens occasionally become diagonally carinated like Cypricardia 
rhombea, Phillips (vide Pl. XIV, fig. 21). The specimen represented by the figure last 
cited, the largest one I have procured, is upwards of an inch in width. 
It occurs, but rarely, in the Shell-limestone of Tunstall Hill, Ryhope Field- 
House-Farm, and Humbleton Quarry. 
Genus Pleurophorus, King, 1848. 
Diagnosis.—< Form mequilateral: cartilage external: anterior adductor muscular 
unpressions deeply excavated, often bounded posteriorly by a ridge: pallial line entire : 
dentition cardinal and posterior: cardinal teeth two in each valve, diverging inwardly, 
and interlocking alternately : postercor teeth limear; the receiving tooth in the left 
valve.” (King.”) 
Type, Arca costata, Brown. 
l A specimen of this species, kindly given me by M. de Verneuil, clearly exhibits the external position 
of the cartilage fulera, a character which has not been overlooked by its founder (vide Geol. Russ., vol. u1, 
p. 316): it is therefore clearly neither a Mytilus nor a Modiola. 
2 Catalogue, p. 11. 
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