APPENDIX. 613 



the shell, may with propriety be considered as the type of a 

 group, and be^ defined as follows. 



Sub-gen. euromus, H. and A. Adams. 



Shell oblong, not turreted, cancellated ; spire short, obtuse, 

 last whorl swollen, much larger than the others ; aperture large, 

 elongate. 



Genus cliopsis, Troschel. 



(Fam. PNEUMODERMONI-D.E.) 



Body ovate. Head keeled ; mouth armed with three jaws ; 

 two lateral tentacles. Fins two, oblong, lateral, anterior, with a 

 truncate intermediate lobe. A ciliated ring round the hinder 

 end of the body. 



Ex. C. Krohnii, Troschel, pi. 137, fig. 3. 



The ciliated ring round the base of the head, and the similar 

 ring round the middle of the body, seen in Trichocyclus, are 

 wanting in this genus. 



Vol. i. p. 60. Genus CHELETROPIS. 



Mr. J. D. Macdonald has made us acquainted with the organi- 

 zation of the animal of this genus, rendering its removal from 

 the Pteropods to the Heteropodous family MacgiUivrayiidic 

 necessary. The arms, four in number, are arranged in a cruci- 

 form manner round the head. There are two. tentacles, and the 

 eyes, well-formed, are situated on the outer side of their bases. 

 The respiratory siphon is short, being a simple fold of the 

 mantle. The foot is large and very mobile, and furnished with 

 a small, thin operculum ; it is unprovided with a float. The 

 lingual membrane is of considerable length, with central and 

 lateral teeth, and the mouth is furnished with two file-like tritu- 

 rating plates. The gill is included, long, single, and pectinated; 

 what was formerly described by the observer as naked gills being 

 the ciliated cephalic arms. 



The name Cheletropis must be changed to Sinusir/era, 

 D'Orbigny, which has priority, and the specific name Huxleyi to 



VOL. II. 4 K 



