Turbonitta.] GASTROPODA. 333 



are stopped below the periphery of the last whorl by a spiral thread 

 arising from the suture. Colour white. Spire high, subulate, much 

 higher than the aperture ; outlines very little convex. Protoconch 

 heterostrophe, of 1 smooth and strongly convex whorl. Whorls 8, 

 regularly increasing, but slightly convex ; base flatly rounded and 

 smooth. Suture deep. Aperture subvertical, elongately oval, angled 

 above and narrowly rounded below. Peristome discontinuous, thin 

 and sharp. Basal Up slightly produced, sometimes effuse and sharply 

 angular. Columella somewhat oblique, slightly arcuate. Inner lip 

 but little reflexed, forming a very thin callosity on the parietal wall. 

 Operculum unknown. 



Diameter, 2-5 mm. ; height, 5-75 mm. (type). Diameter, 1-5 mm. ; 

 height, 5 mm. (specimen of 8 whorls). 



Animal unknown. 



Type in the Dominion Museum, Wellington. 



Hob. Throughout New Zealand, from shallow water to 50 fathoms 

 (the type is from Stewart Island) ; Snares and Bounty Islands, in 

 50 fathoms. 



Remarks. This species is exceedingly variable in size, approaching 

 the Australian T. acicularis, A. Ad., but the costae are more numerous 

 and closer together. Such slender forms as 1 mm. by 3-5 mm. and 

 1 -1 mm. by 4 mm. are met with. 



Fossil. Pliocene. 



Genus 3. ODOSTOMIA, Fleming, 1813. 



Odostojnia, Fleming, Edinburgh Encyc., vii, 1813, 76. Type : Turbo pli- 

 catus, Montagu. Odontostoma, Turton, 1829 ; not of d'Orbigny, 1841. 

 Odontostomia, Jeffreys, 1839. Turritostomia, Sacco, 1892. 



Animal elongated, the head large and robust, bearing 2 conical 

 tentacles, with eyes at their bases ; foot depressed, truncated in 

 front ; mentum anteriorly bilobed. 



Shell small, perforate, oval, conoidal or turriculated ; columella 

 with a feeble, oblique, more or less marked plait ; aperture oval or 

 subrhomboidal ; peristome mostly discontinuous. Operculum horny, 

 lamellar, subimbricated, with a median spiral groove, inner margin 

 indented. 



Very small, usually smooth, shells, having the habit of Rissoce, 

 and sometimes found in brackish water. The species are numerous, 

 of universal distribution, from low water to about 700 fathoms. 



Fossil from the Eocene. 



KEY TO SUBGENERA. 



A. Shell without axial sculpture, except growth-lines. 



a. Spiral sculpture absent, or, if present, microscopic . . ODOSTOMIA. 



aa. Spiral markings more distinct, consisting of subequal im- 

 pressed lines ; shell small . . . . . . . . EVALEA. 



B. Shell with axial sculpture. 



a. With axial ribs and a few impressed spiral lines. . . . PYRGULINA. 



aa,. With spiral cords, the interspaces with faint axial threads MENESTHO. 



