472 
THE GEOLOGIST. 
Lipfii 1. — TEnEnRATULA ELONGATA (Permian). 
Interior ol' dorsal valve, with part of the 
ventral one. 
H, Rostral or dental plates of ventral valve. 
S, Sockets of dorsal valve. 
c, h, Hiimu-ijUites. 
L, Lo.>p. 
A, Quadruple impression of the adductor 
muscle. 
Lip:n. 2. — Tekebratula vitrea (recent). 
Interior of dorsal valve, 
rf. Cardinal process. 
h, HinKC-plate. 
Dental sockets. 
L, Loo]\ 
A, Quadruple impression of the adductor, or 
anterior and posterior occlusor muscle. 
Tlic family TerebratiiliDjE comprises many fjcncra and sub-genera; but 
these do not all appear to possess an equal value or importance, and time alone 
will decide how far we are justified in certain of the divisions that have been 
proposed. Professors M'Coy and King are of opinion that Palajozoie Tere- 
bratulse such as T. hadata^ T. mccuhis, and T. vesicularis, should be separated 
from Trrebnit/ila proper (such as T. vitrea, T. carnea, and T. hipUcaia) on 
account of certain peculiarities, or differences, and have respectively proposed 
Semimla and Epithyris, Phillips, as generic denommations for their reception. 
The differences between Tcrehratiila proper and the palaeozoic species above- 
mentioned are chiefly contincd to the presence of promuient dental or rostral 
plates in the one, and their almost total absence iu the other, as well as in certain 
details connected with the hinge-plate. On the otlier hand, the exterior charac- 
ters arc similar ; and in the interior, the loop offers the same dispositions — is 
short and simply attached, the longitudinal branches being united by a trans- 
versal band more or less bent up in the middle, as is seen in Lign. 2. The 
nuiscular impressions are also simDar, as well as the intimate shell-structure. 
Therefore, while provisionally locating the Carboniferous species under Tere- 
hraiala, it will be necessary to bear in mind those small differences observable 
in the rostral cavity of the beak and hinge-plate which appear to distinguish 
the Palseozoic from the Mesozoic species. 
I. — Terebratula hastata. Sowerby. PI. xii., figs. 1, 2. 
Terehrcdnla hastata, J. de C. Sowerby, Min. Con. Tab. 446, fig. 1-3, 1824, and 
Day. Mon. Carb., p. 11, pi. i., figs. 1-12. 
The shell is usually elongated, oval, or obscurely pentagonal, rounded or 
truncated in front, and tapering at the back. The valves are convex, and 
