20. CO^GHY UM—DITHYRA, 4. 



(Jefijjile species. Very numerous specimens are now in our 

 cabinet,, collected from tlieir native positions], and comparing tliem. 

 together, we think tliat the following preserve habits and charac- 

 ters sufficieatl^f per.nianent to entitle them to specilic distinction. 



nigosa. S^xicAVA tcstd oblongd, transvershn, rugpsd, latere antivo sub- 

 angulato truncato hiante. 

 Shell oblong wrinkled transversely, somewhat angular open and 

 tjTuncf^tje at the a»nierior end. 



Tah. nost. 2, fig. 10. 

 Mytilus rugosus. Linn.Syst. Nat. p. 1166. 



Gmelin Syst. p. 3352. 



Turton Linn. Syst. iv. p. 290, 



Pennant, Brit. Zool. iv. p. 235, tab. 66, fig. 1. 



Da Costa, Brit. Conch, p. 223. 



Montagu, Test. Brit. p. 164. 



Donovan, Brit. Shells, iv. tab. 141. 



T«ir^o», British Fauna, p. 164. 



Linn. Trans, viii. p. 105. 



Dorset Gatal, p. 39, tab. 13, fig. 5v 



DiUwyn, Descript. Catal, p. 304i 



Turton, Conch. Diet. p. 113 

 Mytilus lithophagus. Lfinn. Trans, viii. p. 270, tab. 6, fig. 3, 4. 

 Chaniffi pholas angusta. Lister, Conch, tab. 426, fig. 267. 

 Mus. nost. From rocks in Torbay. 



Shell sometimes half an inch or more long, and an inch and a 

 half broad, but is usually about half the size, white or covered 

 witih a brown skin, coarse and rough with transverse wrinkles': 



