154 THE VOYAGE OF H.M.S. CHALLENGER. 



dementia. Gray. 

 dementia papyracea (Gray). 



Vi-mis {?) 2)a]:>ijracca, Gray, Ann. Philosoph., 1825, vol. ix. p. 137. 



Verms papyracea. Wood, Index Test. Suppl., p. 5, pi. ii. fig. 8. 



Clcmentia (gen.) Graj', Synopsis Contents Brit. Mus., 1840, p. 149, and 1841, p. 127. 



Clemeiitia papyracea, Gray, Proc. Zool. Soc. Lond., 1847, p. 184. 



dementia papyracea, Sowerby, Thes. Conch., vol. ii. p. 700, pi. cli. fig. 155. 



Glementia paprjracea, H. and A. Adams, Genera Eec. Moll., vol. ii. p. 433, vol. iii. pi. cis. fig. 1. 



Clementia papyracea, Chenu, Manuel de Conch., vol. ii. fig. 410. 



dementia papyracea, Pfeiffer, Monog. Veneridaj, in Conch. -Cab., ed. 2, p. 254, pi. xxxi. fig. 16. 



dementia papyracea, Kobelt, lUust. Conchy 1., pi. xcvii. fig. 14. 



Artemis {dementia) papyracea, "Woodward, Man. Moll., p. 306. 



Veims hyalina, Philippi, Abbild. und Beschr., Bd. iii. p. 83, pi. x. fig. 6. 



dementia hyalina, Pfeiffer, loc. eit. supra, p. 253, pi. xxxi. figs. 9-13. 



dementia cumingii, Deshayes, Proc. Zool. Soc. Lond., 1854, p. 346. 



dementia moretoniensis, Deshayes, loc. cit., 1853, p. 18. 



Clementia strangei, Deshayes, loc. cit., 1853, p. 17. 



dementia subquadrata, A. Adams, MS. in Mus. Cuming. 



Var. juv. = dementia similis, Sowerby, Thes. Conob., vol. ii. p. 700, pi. cli. fig. 156. 



Habitat. — Torres Strait, iu 3 to 11 fathoms (Challenger) ; Cape York (J. B. Jukes, in 

 Brit. Mus.) ; Moreton Bay, Philippine Islands, and Malacca (Mus. Cuming) ; Japan 

 (A. Adams and Dunker). 



After a careful study of the forms above enumerated I can arrive at no other 

 conclusion than that they all belong to one and the same species. Clementia strangei is 

 jjerhaps the most peculiar among them on account of the regularity and unusual 

 development of the concentric ridges. On the contrary, Clementia moretoniensis is 

 remarkable in having mere indications of such ridges, being merely roughly concen- 

 trically striated and here and there somewhat plicate. The form is apparently very 

 varial)le, judging from the series of specimens in the British Museum, no two specimens 

 being absolutely alike in this respect. On the other hand, the hinge appears to be very 

 constant in character, and the jDallial sinus and muscular scars are not subject to any 

 important variation. 



It is very probable that the shell described and figured by Chemnitz (Conch. -Cab., 

 voh xi. p. 219, pi. cc. figs. 1959, 1960) as Mactra vitreais, the same species as that under 

 consideration. The fact of it belonging to the genus Clementia has already been 

 referred to by Philippi, Deshayes, and Pfeifier. 



