CO^CH\LlA.—niTHYRA. 1 



dinal rib, aud on the margin above the teeth is a large rough 

 wrinkled tubercle. 



In its outline this species has a great resemblance to the Pholas 

 parva, but differs in the following particulars. 



The shell is thicker and stronger ; the valves are divided in 

 the middle by a longitudinal groove, and have a corresponding 

 rib on the inside ; the transverse ribs are more numerous, and 

 rougher ; the gape is more orbicular, not produced into a beak, 

 and in consequence the extremities of the valves meet close to- 

 gether behind; the tubercles on the inside are rough with 

 wrinkles; and the accessorial valve at the back is truncate -and 

 not pointed at the end, and reaches to the anterior extremity of 

 the shell. 



crispata. Pholas tcstd ovato-ohlongci, extreinitatibus hiantissimis, mar- 

 gins supra denies mutico. 

 Shell oval oblong, very open at both ends, the margin above 



the teeth smooth and without laminar process. 

 Pholas crispata. Linn. Syst. Nat. p. Ill 1. 

 , Gmelin, Syst. p. 3216. 

 Turton, Linn. Syst. iv. p. 173. 

 Pennant, Brit. Zool. iv. p. 157, tab. 43. fig. 2. 

 Chemnitz, viii. p. 369, tab. 102, fig. 872 to 874. 

 Montagu, Test. Brit. p. 23. 

 Donovan, Brit. Shells ii. tab. 62. 

 Turton, Brit. Fauna, p. 145. 

 hinn. Trans, viii. p. 32. 

 Dorset Catal. p. 27. tab. 3. fig. 4. 



4. 



