130 Dr. J. E. Gray on the Division of Ctenobranchons 



a. Pp-amidellina. Shell turrited. Obeliscus, Odostomia, Eu- 

 lima, Aclis, ? Stylina. 



b. Tylodinina. Shell subspiral. Tylodina. 



Cerithiopsis of Forbes and Hanley, tab. 00, if accurately de- 

 scribed, must form a new family in this section. 



Fam. 19. Architectomid.e. Tentacles folded, with the suture 

 below ; eyes sessile on upper surface of their base [Eydoux) . Gill- 

 cavities divided by a longitudinal fold ; foot moderate, truncated 

 in front, rounded behind {Quoy). I have not been able to examine 

 the animal of this family, nor has the proboscis been figured, but 

 the position of the tentacles as given by Quoy, and with more 

 detail by Eydoux, lead me to believe that it is furnished with one. 



a. Operculum ovate. Architedoma. 



b. Operculum circular. Torinia. 



Suborder II. Rostrifera. 



Section 1. Gymnoglossa. Lingual membrane and teeth none ; 

 operculum none. 



Fam. 20. Cancellariad^. Mantle enclosed; pillar of shell 

 folded ; operculum none. Admete, ? Cancellaria. 



Section 2. Toxoglossa. Lingual membrane with two series of 

 subulate elongate, often barbed, lateral teeth (fig. 9). 



Fam. 21. Conid^. Teeth barbed; mantle enclosed; oper- 

 culum ovate, nucleus apical. Conns. 



Section 3. Digitiglossa. Teeth on lingual membrane in seven 

 rows, 3 • 1 • 3 [or perhaps five rows, 2 • 1 * 2 ?), the central teeth 

 triangular, recurved, ^-toothed ; lateral teeth converging, inner co- 

 nical, recurved; the outer large, broad, ovate, with numerous long, 

 linear, equal, curved digitations on the upper edge (fig. 10). 



Fam. 22. Amphiperasid^. Operculum none ; mantle lobes 

 expanded, covering the shell, bearded externally ; shell, edge of 

 outer lip inflexed. Amphiperas. 



The black colour on A. ovum washes off when in spirits. 



Section 4. Tseniglossa. Lingual membrane with seven series 

 of teeth (3 • 1 ■ 3), the central broad, the lateral converging, the 

 inner often broader ; outer lateral conical, except in Viviparidce 

 (fig- ")- 



A. Operculum subannular or none ; mantle furnished with a 

 siphon, and shell with a canal in front. 



* Eyes sessile, on the outer side of the base of the tentacles. 



Fam. 23. Cyprjead^. Operculum none ; mantle lobes ex- 



