Myochama, — Cleidothcet'us. 97 



Myochama anomioides. 

 Tab. Supp. xlii. f. 1, 2, 3, 4. 

 M, testd rosed, tenui, fragili, costis promijientibus radiantibus dichoto- 

 mis ; valvd liberd valde convexd ; umbonc extra apicem valvce altercB 

 prodncto ; epidermidc tenui, pellucidd ; long. \\, lat. -^^, alt. ^V. 



Shell rose-coloured, thin, fragile, ornamented by prominent radiating 

 dichotomous ribs. Free valve extremely convex, the umbo projecting 

 beyond the apex of the other. Epidermis thin and transparent. 



The shell described above adheres to a smooth species of Pectunculus ; 

 some specimens are attached to Trigonia* pectinala, in which case the 

 natural ribs are crossed by others still more prominent, corresponding 

 with those of the shell on which they have grown. 



CLEIDOTH^RUS.f 



Testa suhmargaritacea, incequivalvis, adhcsrefis. Cardo, denle conico 

 in valvd liberd, in fossulam alterius valvce inserto, claviculd testaced 

 elongatd recurvd, cartilagine connexd, et in cicatriciproftcfldd infra 

 utrumque umbonem insertd. Impressiones musculares, in utrdque 

 valvd duts, laterales, antica prcelonga, postica sub-orbicular is. Im- 

 pressio muscularis pallii integra. Ligamentum externum. 



Shell somewhat pearly, ineequivalve, adhering. Hinge with a small 

 conical tooth in the free valve, fitting into a corresponding pit in the 

 attached valve. A testaceous, elongated, curved clavicle, connected by 

 cartilage, is inserted in a deep cicatrix under each umbo. Muscular 

 impressions two, lateral, the anterior lingulate, the posterior suborbicu- 

 lar. Muscular impression of the mantle entire. Ligament external. J 



* It may not be thought irrelevant to mention that Trigonia must be re- 

 moved from the situation Lamarck lias given it, between the Arcaceae and 

 Naiades, to the Cardiaceae ; having seen the living animal, I am convinced it 

 bears the nearest affinity to that family. 



f From the Clavicle in the hinge. 



J Since this Article was sent to press, it has been ascertained that De Roissy 

 has named and characterized this remarkable genus, though evidently from 

 incomplete specimens. He has called it in French " Camosirie" a name so 



Vol. V. ct 



