(32 Art. 6. — M. Yokoyaina : 



whorls preserved are five, but their original number seems to have 

 been at least three more. The height, if perfect, would be about 

 lo millim; the diameter or breadth is 5 millim. 



This species lias a great resemblance to Tiophon murlcatus 

 (Mont.) of the North Atlantic (Forbes and Hanley, British 

 Moll., vol. Ill, p. 439, pi. CXI, figs. 3, 4) and of the English 

 Crag (Wood, Crag Moll., Univ., p. 50, pi. VI, fig. 5), but is 

 chiefly distinguished from it by the ribs becoming obsolete on the 

 body-whorl and the inner lip being smooth within. 



Fossil occurrence. — Miyata Zone (Yamagayado in Kami- 

 ll iyata). 



55. Trophon inerrais, (Sowerby). 

 Pl. III. Figs. 21-26. 



Trophon inermis. Kobelt in Syst. Conch. Cab. Martini u. Chemnitz, vol. HI, pl. 2, Purpur- 

 schnecken, p. 287, pl., 71, fig- 12. Trton, Man. Conch., vol. II, p. 119, pl. 36. fig. 417. 



Murex inermis. Sowerby, Proc. Zool. Soc. London, 1840, Conch. III. fig. 87. Reeve, 

 Conch. Icon. sp. 152. 



Shell rather solid, moderate in size, angulate-f usiform ; whorls 

 eight, shouldered, with shoulders angular; surface above the 

 shoulders obliquely sloping, smooth, surface below them per- 

 pendicular, with one, rarely two. spiral threads, while on the 

 body-whorl there are six to seven such threads with fine inter- 

 stitial spiral lines; threads as well as lines may DT3 very indistinct 

 and nearly obsolete. Varices more or less lamellar, spiny at the 

 shoulders usually decreasing in number from the upper whorls to 

 the lower, there being generally four or five on the body-whorl, 

 but rarely up to eight in which case the number remains tolerably 

 constant on all the whorls. Points of intersection of varices and 

 spiral threads on the body- whorl often elevated into blunt teeth. 

 Aperture oval, slightly angular at the posterior corner. Canal 

 moderate in length, narrow, open, somewhat bent. Inner lip 

 smooth, covered by a thick callus with its outer edge usually free. 

 Below the callus and by the side of the canal, there is often a 

 short tubular process oblique or parallel to the latter and formed 

 by the folding of the outer shell-layer. Outer lip thickened hy an 

 external varix, smooth within. Proportion of height to breadth 



