120 TIIE VOYAGE OF H.M.S. CHALLENGER. 



being flat on their upper surface, and rising roundly from the suture. Apex very small, 

 tabulated. Whorls 4, of very rapid increase, very strongly keeled by the canal-ridge, and 

 angulated by the largest and highest thread ; the base is very tumid. *SW«?"e rectangular. 

 Month oval, very oblique. Outer lip runs in straight lines and angles, but is somewhat 

 curved on the base. Inner lip very thin and very short on the body, extremely retiring, 

 being cut quite away, so as completely to expose the umbilicus, concave on the pillar, where 

 it is sharp edged ; in front it is subtruncate and slightly twisted, but passes on into the 

 outer lip-edge at the umbilical carina. Umbilicus large, defined by a keel, shallow. 

 Puncture very long and narrow, blunt and rounded at the upper end, and extending to a 

 long fine point in front ; it opens on the top of a swollen ridge ; it has no projecting lips 

 on the inner side of the shell, but is produced there in a long narrow furrow. L. 0'052 in. 

 B. 0-062. Mouth, length 0*04, breadth 0'032. 



The young of this species, it is almost certain, will be taken some day for a Trochus, and the 

 adolescent for a Scissuretta, the great length of the old canal and the open foramen being peculiarly 

 deceptive. In this state, when nearly full-grown, it is singularly like Scissuretta costata, D'Orb., 

 from the Mediterranean, but its sculpture is different, the mouth is larger, and the umbilicus is 

 wider and yet more shallow. 



9. Homalogyra, Jeffreys, 1867. 



As a question of mere priority Ammonicerina, Costa, is earlier than Dr Gwyn Jeffreys' name for 

 this genus; but we have already among the mollusca Ammoceratita, Lam., Ammonoceratite, Lam., 

 Ammonoccras, Lam., and Ammonocerus, King. Any man who can keep all these five distinct must 

 have one of those memories which is ordinarily associated with deficiency of judgment, and which in 

 any case must put him quite out of practical sympathy with his fellows. 



Homalogyra, atomus (Philippi). 



Truncatella atomus, Philippi, Archiv f. Naturgesch., 1841, vol. vii. pt. 1, p. 54, pi. v. fig. 4. 



„ „ Philippi, Enum. Moll. Sicil., vol. ii. p. 134, sp. 4, pi. xxiv. fig. 5. 



Skenea nitidissima, Forbes and Hanley, Brit. Moll., vol. iii. p. 158, pi. lxxiii. figs. 7, 8 (but not of 



Adams). 

 Homalogyra atomics, Jeffreys, Brit. Conch., vol. iv. p. 69, sp. 1, pi. i. fig. 5, and vol. v. p. 209, pi. lxx. 



fig. 2. 

 Spira nitidissima, Weinkauff, Conch, d. Mittelm., vol. ii. p. 266. 

 Homalogyra atomus, Montcrosato, Enumeraz., p. 28. 



„ „ Sars, Mod. Reg. Arct. Norv. p. 215, No. 128, pi. xxii. fig. 21, and pi. viii. (bis) 



fig. 1 (radula). 



Station 145. December 27, 1873. Lat. 46° 43' S., long. 38° 4' 30" E. Between 

 Marion Island and Prince Edward Island. 140 fathoms. Volcanic sand. 



Habitat. — From Vadso on the Varauger Fjord, east of the North Cape (Sars), to 

 Madeira (Watson), and the Mediterranean (Jeffreys). 



