274 GINGLYMACONCHA. MYAD&. 
Young shells are often covered with a lead-coloured epi- 
dermis. 
Genus 22. PSAMMOPHILA. 
Shell elongate, recurved behind the umbones; the valves 
convex ; umbones before the middle of the back; epidermis 
antiquated, thin ; hinge in both valves with a tooth, having its 
apex notched, placed before the ligament. 
PSAMMOPHILA SOLENOIDES. 
Shell somewhat ventricose, with concentric antiquated striz. 
Mactra hians, Mont. Test. Brit. 101; M. & R. Trans. Linn. 
Soc. vul. 74; Dill. Desc. Cat. 146; Turt. Conch. Dict. 
85; Flem. Edinb. Encyel. vii. 93. 
Lutraria Solenoides, Zam. Syst. des Anim. sans Vert. 120 ; 
Hist. Nat. des Anim. sans Vert. v. 468. 
It is common at the mouth of the Truro river, and on 
several parts of the Cornish coast. It occurs likewise in the 
Kingsbridge Estuary. Length five inches; height two and 
a half inches. 
Genus 23. ORONTHEA. 
Shells suborbicular ; the umbones central and recurved ; the 
valves convex ; the hinge in one valve with one recurved tooth, 
in the other two teeth* ; in each valve is an elevated lamella. 
ORONTHEA MONTAGUANA. 
Shell subglobose, semitransparent, transversely striolated ; 
epidermis shining. 
Mya suborbicularis, Mont. Test. Brit. 39; Flem. Edinb. 
Encycl. vii. 88; Dill. Dese. Cat. 55. 
Tellina suborbicularis, Zurt. Conch. Dict. 179. 
* T have observed in different individuals of this genus, that the single 
tooth is sometimes in the right, then in the left valve, and the contrary. 
There are several entire species of this genus in the collection of Lord 
Tankerville. 
