MYA. 16-"> 



MY A, Linnaeus. 



M. TRUNCATA, Linn, et Auctorum. 

 M. truncata, Brit. Moll. i. p. 163, pi. 10. f. 1, 2, 3 ; (animal) pi. H. f. 1 . 



Animal elongated, subcompressed ; mantle pale brown, 

 closed throughout, except an anterior fissure for a moderate 

 tongue-shaped, yellowish-white foot, with a byssal groove, and 

 being also produced into a long brown sheath covered with a 

 dark rugose epidermis, under which the skin is white ; it can 

 be extended to double the length of the shell ; when con- 

 tracted it presents the aspect of a mass of close-set annular 

 corrugations ; the sheath also contains the anal and branchial 

 siphons, which are united to their terminations, and scarcely 

 appear beyond the walls of the common envelope ; the former, 

 besides the usual exsertile valve, has about fifteen short dirty- 

 white cirrhi, with as many still shorter between them ; the lat- 

 ter has twenty similar filaments, with intermediate short ones. 

 There are on each side a pair of pale brown branchiae, rather 

 narrow, the upper being somewhat less in depth; they are 

 well pectinated on both surfaces, and their points enter the 

 branchial sheath, but not to near the extent of the Pholades ; 

 the two pairs of palpi are large, basally broad, triangular, of 

 excessive thin texture, marked with fine short brown minute 

 dots, and end in a sharpish point ; they are connected toge- 

 ther by labia coasting the buccal orifice, and are visibly pec- 

 tinated 011 both sides. The liver is dorsal, granular and yel- 

 lowish-green, having the ovarium in contact anteally and 

 ventrally. The stylet and stomachal attritor are present. 



This animal is a littoral species, inhabiting the shingle, and 

 the sandy estuaries. It is also taken alive in the coralline zone. 



Bath, 21st January, 1851. 



I have stated above, that the foot has a byssal groove ; a 

 careful examination of a lively specimen sent me this day from 

 Exmouth, proves that I was mistaken ; the foot, though rather 

 smaller in proportion than in the next species but one, the 

 My a oblonga, nobis, the " Lutraria " of authors, is, like it, 

 without a trace of byssal groove ; the branchiae and palpi of 

 our present species, the type of the family, present the same 



