(>2tl UA-iTROPOJJA. 



tricuspid ; lateral teeth bi- or tri-cuspid, in the latter case the inner 

 cusp is minute ; marginal teeth aculeate, with 1. 2. or 3 ctitting- 

 points. 



Shell almost, completely covered by the mantle, or internal. 



Genus 1. OTOCOXCHA, Button, isxj. 



(Horoitclui. Hutt., T.N.Z.I., xvi. 1883 (1884), 199. Type: Vitrhin dimi- 

 diata, Pfr. 



Animal limaciform. much too large to withdraw into the shell : 

 mantle rather anterior, broadly expanded over the shell, leaving an 

 elongated central opening ; no locomotive disc, nor mucous caudal 

 gland. Jaw distantly furrowed. 



Shell very flat, transparent, partly external, of few rapidly increas- 

 ing whorls ; aperture horizontal. 



This genus, represented by a single species, is precinctive to New 

 Zealand, but it is still open to question whether it is really distinct 

 from Vitrinoidea, Semper, from the Philippines. The external cha- 

 racters all agree with Semper's genus. 



1. Otoconcha dimidiata, Pfeifier, 18f>:>. Plate 25, tigs. 2. 2a. 



Vilrina dimtdtatn, Pfr., M.H. Viv.. iii, 1853, 6; P.Z.X., 1852 (1854), o<> : 

 Conch. Icon., xii, Vitrina, pi. II). f. 72 ; Cat, Pul. Brit. Mus., 71 ; Hector, 

 Cat. Land Moll. N.Z., 2; M.N.Z.M., 12. Ucltcariott dhniJnitus, Pfr., 

 Nomencl. Hel. Viv., 32 ; Man. Condi. (2), i, 181, pi. 42, f. 22. 

 Otoconcha dunidi/iin, Pfr. : Huttcm, T. N.X.I., xvi. 199 ; Hedley and 

 Suter, P.L.S. N.S.W. (2), vii, f',34 ; Suter, -J. de Conch., xli,' 283; 

 Index. (>5. \'itrinoi>fiif< (V it ri n^i<l<n , ilitnidinln. 1'fi. : Suter, T. X.Z.I., 

 xxiii, 94. I'iln'iundca dimidiata, 1'iV. Sulcr, I.e., xxiv. 274. 2s5. 



She/I much depressed, periphery ovate, very thin. 

 with minute arcuate striae, silky, shining, pale-horn colour. Spire 

 nearly flat. Whorls 2|, which are open beneath, and with a narrow 

 membranous edge. Aperture horizontal, as large as the whole shell. 

 Peristome simple, with regularly curved margins. 



Diameter Maj., 5mm. ; min., 3-5 mm. : height, 1-25 mm. 



Animal limaciform, with an oval anterior visceral hump, contain- 

 ing the shell. Mantle smooth. Sides of the long and narrow fool 

 with a distinct peripodial groove, and distant oblique grooves above. 

 the whole surface minutely wrinkled. ( 'uluur yellowish, the mantle 

 mottled with brown, usually with a dark-brown streak on the left 

 anterior part, posterior edge of mantle-slit with a few blackish spots ; 

 foot more or less marbled with black or brown, the lateral grooves 

 dark-coloured ; margin below the peripndial groove whitish ; sole 

 spotted with black. Tail long, narrow, sharply angled above, and 

 ending in a fine point. Sole narrow, simple. Ucnital orifice behind 

 the right ociiliferous tentacle. Respirator;/ onjirc in an oval slit on 

 the right anterior side of the mantle. 



Length of animal, about 25 mm. 



