450 GASTROPODA. [Pectinibranchia. 



last is slightly ventricose, long, attenuated in front. Suture oblique, 

 slightly impressed, irregular. Aperture long, but not wide, oblique, 

 with its two sides nearly parallel, bluntly pointed above, ending below 

 in a broad, shallow, slightly emarginated, minutely bordered canal. 

 Outer Up patulous, thin, but expanded and rounded at the edge ; it 

 rises on the penultimate whorl at its junction, and is here drawn back 

 into a slight sinus with a very reverted edge. Columella perpendicular, 

 with 4 not strong, equal, concealed, pale-coloured, very oblique plaits ; 

 obliquely cut off, twisted and rounded in front into a prominent thin 

 point. Inner lip spreading widely as a thin glaze on the body. 

 (Watson.) 



Diameter, 31-6 mm. ; height, 70mm. Angle- of spire, 42. 



Animal unknown. 



Type in the British Museum. 



Hab. Two hundred miles west of Cape Farewell, in 275 fathoms. 



Remark. The form of the shell, the rnamillary protoconch with 

 rounded nucleus, and the number of plaits remove it from Cymbiola. 



Fain. OLIVIDJE, d'Orbigny. 



Animal having the foot divided anteriorly by a transverse groove 

 and the fore part extended beyond the head ; eyes, when present, 

 on the middle of the tentacles ; a posterior pallial tentacle. Lobes 

 of the foot usually reflexed over the sides of the shell ; siphon recurved. 

 The radula has the formula 1 + 1+1 ; the central tooth transverse, 

 multicuspidate, laterals unicuspidate, triangular or unciform. 



Shell smooth, polished, porcellanous, without epidermis, subcylin- 

 drical or subfusiform ; aperture oblong, notched at the base ; colu- 

 mellar lip, sutures, and spire more or less covered with a callous 

 deposit. Operculum present or absent. 



The animals are mostly burrowing in sand. 



Fossil from the Cretaceous. 



Genus 1. ANCILLA. Lamarck, 1799. 



Ancilla, Lam., Mem. Soc. Hist. Nat. Paris, 1799, 70. Type: .4. cfnna- 

 inoinea, Lam. AnciUorin. Lam., 1811. Ancillus, Montfort, 1810. An- 

 inda.r, Roissy, 1805. Amalda, H. and A. Adams, 1853. Sparella, Gray, 

 1857. Sandetta, Gray, 1857. 



Animal having an elongated foot, bifurcate posteriorly, the lateral 

 lobes reflexed over the shell ; the anterior part of the foot (propodium) 

 triangular, with a median longitudinal groove above ; tentacles small, 

 without eyes ; siphon elongated. Central tooth of radula with 3 

 well-developed cusps and a few intermediate small denticles. 



8hell oblong, occasionally acuminate, smooth and polished ; suture 

 sometimes canaliculate, but more frequently covered over by callus, 

 sometimes completely hiding the spire ; columella excavated, twisted, 

 and carrying several plications towards the base, which are not hidden 



