744 CLASS xn. 



Cyclas BRUG. (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., BLAINY. Malacol. PL 73, fig. i, 

 PFEIFFEB Systemat. Anordn. u. Beschr. deutscher Land- und Wasserschn. 

 Cassel, 1821, 4to, Tab. v. figs, i, 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 trachea;, 

 which in the animal of these species are short and grown together. Sp. 

 Cyclas obliqua LAM., Cycl. fontinalis LAM., Cycl. obtusalis LAM. 



Family XV. Lucinacea. Mantle open anteriorly, concrete 

 posteriorly, and furnished with branchial aperture and single anal 

 trachea, or produced into two tracheae 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. 



Cyreno'ida 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 tracheae concrete and four labial palps. 



Sp. Cyrenoida Dapontia JOANNIS, GUERIN 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 DE 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 BRUG. Shell orbiculate, transversely striated, subequi- 

 lateral, with points short, acuminate, incurved forwards. Hinge vari- 

 able. Animal (Loripes POLI) with foot very long, vermiform, respira- 

 tory trachea foraminiform, anal conical, retractile by invagination. 



Sp, Lucina lactea LAM., Tellina lactea L., Encycl. meth., Vers. PL 286, fig. 

 i, POLI Testae, utr. Sic. I. Tab. xv. figs. 26 29 ; hab. Mediterranean ; 

 Lucina pensylvanica LAM., Venus pensylvanica L., D'ARGENV. Conchyl. 

 Tab. 21, fig. N, Encycl. meth., Vers. PL 284, fig. i ; hab. in the ocean at the 

 coast of N. Amer. ; Lucina divaricata LAM., Tellina divaricata L., POLI 

 1. 1. fig. 25, Encycl. me'th., Vers. PL 285, fig. 4, DESHAYES Conchyl. PI. 16, 

 figs. 9 1 1 ; hab. in Mediterranean, &c. 



