18 



CONCHYLIA—DJTHyj?^. 3. 



with a tube of adhesion, by which it attaches itself firmly to the 

 outer case. 



The principal points of discrimination between this genus and 

 that of the Pholas are, not merely the want of accessorial valves, 

 as has been usua.Iy supposed, but the essential difference of the 

 teeth, and in being furnished with a strong permanent coriaceous 

 ligament uniting the valves together. 



pholadls. 

 1, 



Gastroch^na valvis latere antico postici conniventibus, umbonibut 



subterminalibus prominulis. 

 Shell with the valves closing together behind at the anterior end, 



the beaks nearly terminal and rather prominent. 

 Tab. nost. 2, fig. 8 and 9 

 Gastrochaena cuneiformis. Spengler, ii. p. 179, fig. 8 to 11. 



Pholas hians. 



Mya dubia 



Mya pholadia. 



Mytilus ambiguus. 

 Chama parva. 



Chemnitz,, x. p. 364, tab. 172, fig. 1678. and 



1679. 

 Pennant, Brit. Zool. iv. p. 165, tab. 47. 



Turton, Linn. Syst. iv. p. 179. 



Dorset Catal. p. 27, tab. 1, fig. 11. 



Linn. Trans, viii. p. 33. 



Donovan, Brit. Shells, iii. tab. 108. 



Turton, Brit. Fauna, p. 146. 



Wood, Conch, p. 102, tab. 25, fig. 2 and 3. 



Turton, Conch. Diet. p. 104. 



Montagu, Test. Brit. p. 28 and 559, and 



suppl. p. 20. 



Dillwyn, Descript. Catal. p. 304. 



Da Costa, Brit. Conch, p. 234. 



Mus. nost. In rocks and stones, Torbay. 



