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



Cryptodon luzonicus, u. sp. (PI. XIV. figs. 5-5a). 



Testa parva, tenuis, insequilateralis, globosa, obliqua, rotuude subquadrata, alba, 

 epidermide tenuissima lutescente induta, concentrice subdistanter graciliter lirata. Um- 

 bones nivei, nitidi, promiueutes, incurvati, antrorsum involuti. Cardo fere edentulus, 

 valva dextra tuberculo miuuto dentiformi sub apicem instructa. Pagina interna nitida, 

 radiatim tenuissime striata, margine simplice circumdata. 



This species is very thin and fragile, rather convex, and of an oblique growth, the 

 anterior side being produced so as to give the shell an inequilateral aspect. The outline 

 is roundish -square, but interrupted above by the prominent umbones. The front side is 

 higher and less curved than the posterior, and the dorsal line on the anterior side is 

 longer and not so sloping as the hinder margin. The shell is pure white, but clothed to 

 a great extent with a thin yellowish slightly fibrous epidermis. It is sculptured with 

 numerous fine concentric lirse, which are not nearly so broad as the interstices between 

 them, and gradually become obsolete upon the smooth snow-white beaks, which are rather 

 prominent, glossy, well curved over towards the front, the apices, however, having about 

 a central position on the dorsal line. In addition to the liras, the entire surface of the 

 valves has the appearance, under a strong lens, of being minutely dotted all over with 

 small pellucid spots. The hinge is almost entirely destitute of teeth, there being only a 

 very small tubercle on the hinge-line of the right valve immediately under the tip of the 

 beak. The ligament is placed on the hinge-line between the valves, so that it is partly 

 external and partly concealed. The interior of the valves is glossy hwt very finely 

 striated in a radiate direction, and the outer margin is simple and smooth. The scars 

 and paUial line are indistinct. 



Length 6^ mm., height 6^, diameter 5. 



JZ^at/tof.— Station 205, ofi" the west coast of the Island of Luzon, Philippines, in 1050 

 fathoms ; blue mud. 



Cryptodon jlexuosus (Montagu). 



Tellina flexuosa, Montagu, Test. Brit., p. 72. 



Ludna flcxuosa. Reeve, Conch. Icon., vol. vi. pi. xi. fig. 62. 



Lucitia flexuosa, Forbes and Hanley, Brit. Moll., vol. ii. p. 54, pi. xxxv. fig. 4. 



Axinus flexuoMis, Jeffreys, Brit. Conch., vol. ii. p. 247, and vol. v. p. 179, pi. xxxiii. fig. 1. 



Axinus flexuosiis, Jeffreys, Proc. Zool. Soc. Loud., 1881, p. 701. 



Axmus fli'xuosus, G. 0. Sars, Moll. Reg. Arct. Norv., p. 59, pi. xix. figs. 4, a, h. 



Cryptodon flexuoms, Turton, Conch. Dithyra, p. 121, pi. vii. figs. 9, 10. 



Habitat. — Station 75, of Fayal, Azores, in 450 fathoms ; volcanic mud. 



Only a single valve which undoubtedly belongs to this species was dredged. It 

 belongs to the variety named polygona. 



For the distribution of this species, see Dr. Gwyn JeS"reys' paper. ^ 



1 Proc. Zool. Soc. Land., 1881. 



