780 



Ast. testa solida^ ovali, costellis magnis subgradiformibus, mar- 

 gine dorsali elongate, declivi; margine ventrali intus (semper?) 

 crenuluto. 



The ribs are large and step-like, and the hinder dorsal margin 

 slopes in a long curve from the apex to the ventral corner. In 

 other respects like sulcata. In Mr. Cuming's collection is a spe- 

 cimen named Mortovi (not fully developed?), with the ventral 

 margin smooth ; but it has so exactly the character of the A. tin- 

 data (which is crenulated) that it must be considered another case 

 of Scotica versus sulcata. 



North America. 



5. AsTARTE CREBRicosTATA (pi. clxvii. f. 10), Forhcs, Ami. 

 Nat. Hist. vol. xix. p. 98. pi. 9. f. 4. 



Ast. testa compressa, postice subtruncata, suboblonga, valde 

 insequilatera, costellis concentricis numerosissimis postice sub- 

 evanidis, margine intiis crenulato; impressione paUii prope mar- 

 ginem posita. 



The state of the hitherto found specimens is strongly suggestive 

 of pleistocene beds ; but no such beds have been found near the 

 place where A. crehricostata was first found. Only single valves 

 (we figure Mr. Hanley's specimen) have been dredged in deep 

 water at Zetland and Skye. 



North Britain. 



6. AsTAETE suBiEQUiLATERA (pi. clxvii. f. 13), Sowerbi/, jun. 



Ast. testa compressa, subovali, antice breviuscula, declivi, pos- 

 tice subtruncata, costellis numerosis, distinctis ; margine crenato. 



It is not unlike A. creljricostata, but much more equilateral. 

 The ribs are not quite so numerous, and the pallial impression is 

 not near the ventral margin. 



Mr. Cuming's collection. Newfoundland. 



7. AsTARTE Arctica (pi. clxvii. f. 17, 18, 20), Grat/. Cras- 

 sina Arctica, Grai/, App. Captain Parry's Voyage. Y. borealis, 

 Chemn., Nilsson (not Linn.). Astarte cyprinoides, Duval, Rev. 

 Zool. ; Ranley, Eecent Shells, Suppl. pi. 14. f. 40. C. corrugata, 

 Broton. A. Japonica, Jay ? 



Ast. testa plerumque ovali, subdepressa, insequilatera, versus 

 apicem et ad medium concentrice irregulariter et obsolete corru- 

 gata ; margine tenui, intiis Isevi. 



After studying for some time a number of specimens, young 

 and old, in various conditions and variously named as above, some 



