Cyclostremdla.] GASTROPODA. 161 



callosity. Umbilicus of the same aspect as the sunken spire. Oper- 

 culum unknown. 



Diameter Maj., 2 mm. ; rain., 1-6 mm. : height, 0-7 mm. 



Animal unknown. 



Type in my collection. 



Hob. Snares, in 50 fathoms (Captain Bollons). 



Remark. The suture of this species is not canaliculated, hence the 

 circular aperture, not angled above. 



Fam. TURBINID^C, Gray. 



Animal with an oval, broad, or narrow foot, truncated anteriorly ; 

 rostrum rather short, truncate ; tentacles long, slender, cylindrical, 

 the eyes on peduncles at their exterior bases. Across the front of the 

 head, between the tentacles, extends the more or less developed " veil " ; 

 and from a point below the tentacles a fleshy ridge (the " epipodial 

 line ") extends backward parallel with the margins of the foot, and 

 bearing usually several slender cirri on either side. 



Radula usually with the formula oo + 5+ 1 + 5 + , but some- 

 times lacking the median and 1 outer lateral tooth. The lateral teeth 

 are all of nearly the same form. Jaws usually present. 



Shell turbinate or trochiform, generally solid, smooth or rugulose ; 

 aperture circular, oval, or subtetragonal ; peristome simple ; oper- 

 culum calcareous, heavy, flat or concave, with a thin corneous layer 

 internally, the nucleus multispiral and either subcentral or at the 

 margin. 



Ordovician to Recent. 



They are mostly littoral in station, and inhabitants of tropical and 

 subtropical seas. They are herbivorous. 



KEY TO GENERA. 



A. Shell turbinate, large, convex below ; operculurn convex 



outside, nucleus near centre . . . . . . TURBO. 



B. Shell trochiform, young carinated and spinose : operculum 



with submarginal or terminal nucleus, generally with ribs 



outside . . . . . . . . . . . . ASTR^EA. 



C. Shell turbinate or globose, small, solid ; operculum multi- 



spiral, concave in the centre outside . . . . . . LEPTOTHYRA. 



Genus 1. TURBO, Linnaeus, 1758. 

 Turbo, L., Syst. Nat., ed. x, 761. Type : T. marmoratus, L. 



Head of animal proboscidiform, slightly extended in front ; ten- 

 tacles long and cylindrical ; the ocular peduncles dilated, outside the 

 base of the tentacles ; epipodial line with a small number of cirri. 



Shell turbinate or depressed, imperf orate or umbilicate ; young 

 not carinated or spinose ; base convex. Operculum flat or concave 

 inside, with 3 or 4 whorls and subcentral nucleus ; outside convex, 

 smooth, tuberculate, or with concentric ribs. 



Numerous species in the Tertiary. 



Living in warmer or tropical seas. 



6-Moll.N.Z. 



