Se Pr are 
Description of Bight new Species of Shells. 107 
resemblance to the Venus gemma of Totten. Indeed I consid- 
ered it as such for some time, until I was able to obtain a view 
of the teeth, which prove it to be a Cyrena. It may, however, 
be also distinguished from the Venus gemma, by its equilateral 
form, and want of crenulations on the margin. The beaks are 
rounded at the summit. It has usually a dark purple mark along 
the posterior margin, which gradually fades off, and the anterior 
portion of the shell is whitish. Occasionally, however, it is 
nearly all purple, but darker towards the posterior margin, and I 
have one specimen which is pinkish. The strie are perfectly 
regular, and at even distances. It is, I believe, the smallest Cy- 
rena yet noticed. vf 
; Genus Moprora.— Lamarck. 
M. elliptica. PI. 1, fig. 2. 
M. testa transversa, ellipticé, sub-inflata, pellucida, purpureo- 
maculata, polita, radiatim striata posticé et antice ; valvulis tenui- 
bus; natibus sub-prominentibus; margine crenulato posticé ac 
antice ; margarita diaphana et nitente. 
Shell transverse, elliptical, sub-inflated, pellucid, marked with 
purple, polished, radiately striate posteriorly and anteriorly ; 
valves thin; beaks somewhat prominent; margin crenulated 
posteriorly and anteriorly ; nacre diaphanous, shining. 
ength ‘07 Breadth -1. Diam. -025 of an inch. 
_ Hab. Delaware Bay. Cabinet of I..Lea. 
~ Remarks.—The area of the valves is divided into three fan- 
shaped compartments by the strie, of which the anterior con- 
tains about seven, and the posterior about twenty-four. The 
purple marks in some specimens are so numerous, as to completely 
cover the shell, while others are nearly free from them. They 
are frequently zigzag. ‘The dorsal margin appears to be slightly 
crenulate. It is strongly allied to the Modiola discors, nexa and 
discrepans, and might be confounded with the young of either 
of those shells. But its size appears constant, as I have taken 
them at various seasons of the year; in addition to which the 
difference in shape and marking, and the want of transverse strie, 
will distinguish it. 
M. puler. Pl. 1, fig. 3. 
M, testa transversa, obovata, levi, polita, viridescente, diaphana, 
‘purpureis omnete; iene emg natibus et 
nentibus, sub-acutis. 
