744 CLASS XII. 
Cyclas Brua. (in part), LAM. Shell ovato-globose, thin, tumid 
at the points. Hinge with teeth very small, sometimes subnull. 
Sp. Cyclas cornea Lam., Tellina cornea L., Buatnv. Malacol. Pl. 73, fig. 1, 
Preirrer Systemat. Anordn. u. Beschr. deutscher Land- und Wasserschn. 
Cassel, 1821, 4to, Tab. v. figs. 1, 2, shell brown-yellow, transparent, blue- 
white within, 4 or 5” large; not rare in the canals of Holland. The 
species of this genus, which is much allied to the preceding, are especially 
found in Europe, but some occur also in other parts of the world.— PFEIFFER 
further distinguishes the genus Pisidium, by the absence of long trachee, 
which in the animal of these species are short and grown together. Sp. 
Cyclas obliqua Lam., Cyel. fontinalis Lam., Cycl. obtusalis LAM. 
Family XV. Luctnacea. Mantle open anteriorly, concrete 
posteriorly, and furnished with branchial aperture and single anal 
trachea, or produced into two tracheze connate from the base 
throughout. Foot cylindrical, elongate, often vermiform. Liga- 
ment external or subinternal concealed between the exsert margins 
of fissure. ‘Two muscular impressions remote, large, with anterior 
elongate. Shell free; hinge variable, in some edentulous, in others 
with two teeth under the point, and one or two lateral teeth. 
Cyrenoida JOANNIS, Cyrenella DesHayes. Shell ventricose, 
corticate. Hinge with two small teeth divergent in right valve, 
and one tooth bifid in left valve; lateral teeth none. Animal 
with two trachez concrete and four labial palps. 
Sp. Cyrenoida Dupontia JoANNIS, GuGRIN Magasin de Zool. 1835, Mollusq. 
Pl. 64. Comp. DEsHAYES, ibid. No. 70; Senegal. This genus counts only 
a few species, all exotic, from fresh water. According to DESHAYES Cyre- 
nella is a fresh-water Lucina, according to Dr JoANNIs, a Cyrena without 
lateral teeth at the hinge of the shell. At all events, this genus is inter- 
mediate between this and the preceding family. 
Lucina Brua. Shell orbiculate, transversely striated, subequi- 
lateral, with points short, acuminate, incurved forwards. Hinge vari- 
able. Animal (Loripes Pot) with foot very long, vermiform, respira- 
tory trachea foraminiform, anal conical, retractile by invagination. 
Sp. Lucina lactea LaM., Tellina lactea L., Encycl. méth., Vers. Pl. 286, fig. 
1, Pow Zestac, utr. Sic. 1. Tab. xv. figs. 26—29; hab. Mediterranean ;— 
Lucina pensylvanica Lam., Venus pensylvanica L., D’ARGENV. Conchyl. 
Tab. 21, fig. N, Hncycl. méth., Vers. Pl. 284, fig. 1; hab. in the ocean at the 
coast of N. Amer.; Lucina divaricata Lam., Tellina divaricata L., Pout 
1. 1. fig. 25, Encycl. méth., Vers. Pl. 285, fig. 4, DesHayEs Conchyl. Pl. 16, 
figs. g—11; hab. in Mediterranean, &e. 
