772 



Pet. testa P.jjJwladiformi similij sed costellis anticis vix elevatis, 

 iuterruptis, acute serratis. 



The front ribs are here reduced into radiating rows of sharp 

 points; still I doubt greatly whether this may not be a mere 

 varietal distinction. 



New Zealand. Mr. Cuming^s collection. 



3. Peteicola gracilis (pi. clxvi. f. 12), Beshayes, Pro. Zool. 

 Soc. 1853. 



Pet. testa T . plioladlformi simili sed longe graciliore, costellis 

 anticis vix elevatis, acute serratis, postice attenuata, striis subob- 

 soletis. 



Sculptured like P. serrafa, but more finely; a much lighter 

 and elongated shell than either it or P. pJioladiformis, still very 

 doubtful. 



Hah. ? Cuming^s collection. 



4. Petricola cultellus (pi. clxvi. f. 2, 5), Beshayes, Pro. 

 Zool. Soc. 1853. 



Pet. testa elongato-angusta, transversa pholadiformi lateraliter 

 compressiuscula inferno convexo-arcuato ; antice brevi posticeque 

 obtusa, hiante albo squahde rufescente longitudinaliter squamulis 

 fornicatis exasperatis ; striis in medio posticeque tenuibus, undu- 

 losis striis incrementi irregularibus interruptis ; umbonibus tumi- 

 duhs approximatis Isevigatis, valvis iutiis candidissimis ; sinu 

 pallii elongato, angusto, apice obtuso. 



The form is similar to that of P. pholadiformis ; it has rather 

 sharp serrated ridges in front ; it is rather depressed, of a very 

 pale fawn-colour, and has the ventral margin rather rounded. 



Ceylon. Mr. Cuming^s collection. 



5. Petricola dactylus (pi. clxvi. f. 4), Sotverby, Gen. of 

 Shells, f. 3. 



Pet. testa inflata, ovali pallide grisea, intiis alba, antice brevi, 

 subacuminata planulatim costellata, medio tumida, costellis latio- 

 ribus, inde subcontracta, costellis numerosis, cancellatis, postice 

 attenuata subtruncata concentrice striata, striis radiantibus obso- 

 letis. 



A very tumid pholadiform shell, differing from P. nivea in 

 being much stronger, and having th'b short front side almost ros- 

 trated, the middle tumid, and the back contracted. The sculp- 

 ture is in flattened ridges to about the middle, then sharper and 

 more numerous, then lost at the back. 



South America. 



