REPORT ON THE LAMELLIBRANCHIATA. 193 



Cryptodon croulinensis (Jeffreys). 



Clausina cwidinensis, Jeffreys, Ann. and Mag. Nat. Hist., 1847, vol. xx. p. 19 ; op. cit., 18.58, 



vol. ii. p. 122, pL V. figs. 2, a-c. 

 Axinus croulinensis, Jeifreys, Brit. Conch., vol. ii. p. 2.50, vol. v. p. 180, \)\. xxxiii. lig. 2. 

 Axinus croidinetisis, Jeffreys, Proc. Zool. Soc. Lond., 1881, p. 703. 

 Axinus croulinensis, G. 0. Sars, Moll. Reg. Arct. Norv., p. 62, pi. xix. fig. 8. 



Habitat. — Station VIII., off Canary Islands, in 620 fathoms ; Station 33, off 

 Bermuda, in 435 fathoms ; and Station 78, off the Azores, in 1000 fathoms. 



A single specimen from the first locality, one valve only from the second, and about 

 a dozen valves from Station 33, is all that was obtained. That from the Canary 

 Islands and the Bermudan valves are hardly so obliquely expanded in front as examples 

 from the Shetland Islands with which I have compared it, and the posterior impressed 

 rays are so much stronger that I feel doubtful whether they may not be specifically 

 distinct. 



This species has been found at the island of Skye, the Shetlands, in deep water in 

 the Atlantic, off the Norwegian coast, in the Mediterranean and the Adriatic. Also 

 found fossil in PUocene and Post-tertiary formations (teste Jeffreys). 



Cryptodon incrassatus, (Jeffreys), var. 



Axinus incrassatus, Jeifreys, Ann. and Mag. Nat. Hist., 1876, vol. xviii. p. 492. 

 Axinus incrassatus, Jeffreys, Proc. Zool. Soc. Lond., 1881, p. 703, pi. Ixi. fig. 7. 



Habitat. — Station 24, off Culebra Island, West Indies, in 390 fathoms ; Pteropod ooze. 



The few odd valves from the above locality have already been referred to this species 

 by Dr. Gwyn Jeffreys in the Proceedings of the Zoological Society. Not having had an 

 opportunity of comparing them with typical examples, I cannot give any positive 

 opinion respecting their identity. Judging, however, from the description in the 

 Annals and the figure in the Proceedings, I feel no hesitation in pronouncing them a 

 well-marked variety, and am almost inclined to hold them specifically distinct. They are 

 rounder and less oblique in form, and consequently more equilateral. The hinge-plate 

 cannot be described as " remarkably thick on both sides," the posterior side in the right 

 valve is not crenulated, nor does the anterior side correspond with the figure. There is 

 but one right valve in the collection, and in this the hinge-line is produced immediately 

 beneath the beak, the minute projection (it can scarcely be termed a tooth) fitting in 

 under the tip of the umbo in the other valve. The front portion of the hinge-plate in 

 this valve is thin, whilst in the left it is a little thickened. The posterior dorsal line in 



(zool. chall. EXP. — PART XXXV.— 1885.) Mm 25 



