BASILISSA-EUCHELUS. 429 



callus on the body is thin and smooth, that within the outei' lip is 

 broad, thick, iridescent, and deeply grooved i)arallel with the 

 external sj)irals, producing four or five ridges between the grooves 

 above the carina and a large number of rather smaller ones 

 below it. The columella is thickened concave and strongly re- 

 flected, its basal extreme terminating in a stout tooth-like twist of 

 the margin, beyond which is a deep sulcus in the callus extending 

 nearly across the base, in the middle of which rises a solitary stout 

 tooth-like ridge. The walls of the umbilicus are nearly smooth, 

 and as regards the individual turns are somewhat concave. The 

 nucleus in this form gives the impression, after a very close scrutiny 

 of several fresh specimens, that it is really laid at right angles to 

 the original axis and half immersed in the first post-nuclear turn. 

 This is masked by the fact that the nucleus proper occupies less 

 than a single turn, and appears thus more normal than it really is, 

 if my suspicions are correct. 



Genus EUCHELUS Philippi, 1847. 



Euchelus Phil., Zeitschr. f Mai. 1847, p. 20, type Monodonta tri- 

 carinata Lam. — Aradasia Gray, Figures of Molluscous Animals, iv, 

 p. 90, 1850, type, E. canaliculatus (^.,=atratus Gm. — Huttonia 

 Kirk, Trans. N. Z. Inst, xiv, p. 282, 1882, type, E. bella Hutton.— 

 Mo)iodonta and TrocJnis in part, of authors. 



I include as subgenera, Tallorbis Nevill and Danilia Brusina, 

 both with considerable hesitation. Of the first I have seen no speci- 

 men ; the latter is well-known as far as the shell is concerned ; it has 

 a corneous mu^^isjotra^ operculum ; the columella twisted above as in 

 typical Turcica or Glancxdus. Its sculpture is like Euchelus or 

 Perrinia. The varixed lip is unique in Trochidre. " Fischer includes 

 it as a subgenus under Clanculus — a position as likely to be correct 

 as that here taken. 



The affinities of Euchelus are not very clear. There is a certain 

 resemblance in aperture and columella to Clanculus, and the deflec- 

 tion of the whorl at the aperture, rather an unusual character in 

 TrochidjB, also favors that genus. There is much likeness to Perrinia, 

 too, in sculpture and aperture, but that group certainly belongs to 

 Turcica as a section, and seems to be close to Calliostoma. 



The following well-defined natural sections may be recognized : 

 Euchelus s. s. Shell turbinate-conic, solid, with thick lip ; spire 

 elevated ; operculum with few whorls, like that of Littorina ; colu- 



