126 Dr. J. E. Gray on the Division of Ctenobranchous 



Suborder II. Rostrifera. Head moderate, with a more or 

 ]ess elongated, produced, contractile, transversely annulated ros- 

 trum ; tentacles subulate, far apart on the side of the rostrum. 

 Essentially phytophagous ; the rostrum is only furnished with 

 contractile muscles, and varies in length and shape; in Struthio- 

 laria it is very long and conical subulate, but it is not retractile 

 like those of the former suborder; the rostrum of Strombi is 

 also elongated, while in some other families it is short and trun- 

 cated; but it is always easily known from the retractile proboscis 

 of the former group ; the lingual membrane is often very long, 

 extending far into the body of the animal. 



The families are the same as those characterized in the ' Figures 

 of Molluscous Animals,' vol. iv. 1850, only placed in different 

 order, to show the characters afforded by the teeth, with some 

 new ones rendered necessary by the examination of the teeth of 

 some genera which had not before been described. 



Suborder I. Proboscidifera. 



A. Hamiglossa. Teeth on lingual membrane in three series 

 (1 • 1 • 1), the central broad, the lateral versatile (fig. 1). 



Fam. 1. MuricidjE. Lateral teeth flat, with a bent-up pro- 

 cess at the end more or less at right angles with the base ; siphon 

 of mantle and canal of shell straight ; foot simple in front ; man- 

 tle enclosed. 



a. Muricina. Operculum ovate ; nucleus subapical within the 

 apex ; varices of shell developed. Murex, Trophon. 



b. Fusina. Operculum ovate, acute; nucleus apical; varices 

 of shell rudimentary or none. Pisania, Colus, Cassidulus, Chry- 

 sodomus. 



? c. Pusionellina. Operculum semiovate ; nucleus in middle of 

 the straight inner edge. Pusionella. Teeth ? 



d. Rapananina. Operculum ovate, blunt ; nucleus elongate, 

 forming the outer or hinder edge. Rapana, ? Chorus and ? Cuma. 



Fam. 2. Buccinid^. Lateral teeth flat, with a bent-up pro- 

 cess at the end more or less at right angles with the base ; 

 siphon of mantle and canal of shell recurved ; foot simple ; mantle 

 enclosed. 



a. Buccinina. Operculum ovate ; nucleus small, near outer 

 front edge. Buccinum. 



b. Nassina. Operculum ovate, acute, nucleus apical. 

 * Operculum entire. Latrunculus, Cominella, Phos. 

 ** Operculum serrated. Bullia, A^assa, tNorthia. 



