GASTROPODA. 265 



1. Caecum digitulum, Hedley, 1904. Plate 15, fig. 9. 



Caecum digitulunt, Hc.lley, Rec. A.M., v, 94, f. 21 in text ; Iredale, T.N.Z.T., 

 xl, 384. 



Shell small, smooth save for very slight growth-lines, thin, opaque 

 dull white, slightly curved, tapering rapidly. Aperture circular, 

 slightly everted. Septum subungulate. (Hedley.) 



Diameter Maj., 0-5 mm. ; min., 0-3 mm. : length, 2-3 mm. 



Animal unknown. 



Type in the Australian Museum, Sydney. 



Hab. Lyall Bay, Cook Strait (type) ; Foveaux Strait (A. Hamil- 

 ton) ; Lyttelton Harbour, under stones at high- water mark (Iredale). 



Remarks. The rapidity with which this species tapers is an un- 

 usual feature (Hedley). The majority of the shells do not taper as 

 rapidly as Hedley's description would imply, nor as his figure shows 

 (Iredale). 



Fossil in the Pliocene of Wanganui. 



Fam. TURRITELLID^J, Clark. 



Animal with a large and prominent head ; rostrum short and broad ; 

 tentacles long, subulate, and diverging, the eyes slightly prominent 

 at their external base ; mantle-margin fringed, with a siphonal fold 

 on the right side ; no siphon ; branchial plume single, very long ; 

 foot very short, truncate in front, attenuated and obtuse behind, 

 grooved beneath ; operculigerous lobe simple. The lingual dentition 

 is very variable ; the marginals may be absent, or their number vary- 

 ing from 1 to 3. (Man. Conch. (1), ix, 192.) 



Shell long, attenuated, many-whorled, not umbilicated, sculptured 

 with spiral stripe or ridges, lines of growth arched and sinuous ; aper- 

 ture rounded or subquadrate, entire ; lip thin, externally flexuous, 

 not thickened. Operculum multispiral. 



Distribution. Found in most seas, from low-water mark to deep 

 water. 



Fossil from the Trias. 



Genus 1. TURRITELLA, Lamarck. 1799. 



Turritdlu, Lam., Mem. Soc. Hist. Nat. Paris, 1799, 4. Type: Turbo 

 terebra, L. 



Shell pyramidal, the numerous whorls spirally striated or ridged, 

 crossed by arcuated growth-lines ; spire very high, aperture oval or 

 subquadrangular, entire, lip thin. Operculum with fimbriated margin- 



Over a hundred species are known, inhabiting all seas, but prin- 

 cipally tropical and subtropical. The fossils number about 400 species ; 

 the genus commenced in the Trias. 



Vernacular Name. Screw- shell. 



