MURICID^. 105 



and Phyllonotus and Chicoreus have the same general facies, 

 although they differ in the number of varices. Owing to their 

 inter-relationships, no attempt to present the groups in succes- 

 sion can he other than exceedingly artificial. 



a. Oj^erculuvi with subapical nucleus. 



* Varices three. 



MUREX (typical). Shell spinous ; spire elevated ; canal very 

 long, narrow, nearly straight. 



PTERONOTUS, Swaiuson. Shell triangular ; varices fin-like or 

 foliated ; canal moderate, closed, somewhat curved. M. trigon- 

 ulus, Lam. (xliii, 2). 



CHICOREUS, Montf. Shell ovate-p3^riform ; varices foliated and 

 sometimes spinose ; canal sljort, curved, wide, nearly closed. M. 

 adustus, Lam. (xliii, 3). 



ODONTOPOLYS, Grabb. Resembles the subgenus Pteronotus in 

 having three varices on each whorl, but distinguished by the 

 crenulations of the outer lip and b}^ having two transverse plaits 

 or folds on the middle of the columella. M. compsorhytics, Gabb 

 (xliii, 4). Eocene ; Wheelock, Texas. 



* * Varices four to ten. 



RHiNOCANTHA, H. and A. Adams. Has the short body-whorl 

 and long canal of the typical Murices ; difTers in having more 

 numerous varices. M. cornutus, Linn, (xliii, 5). 



HOMALOCANTHA, Morch. Whorls rounded and sutures very 

 deep ; varices foliated, and peculiarly produced into expanded 

 digitations ; canal long. M. scorpio^ Linn, (xliii, 6). 



PHYLLONOTUS, Swains. Like Chicoreus, but varices numerous. 

 M. radix, Gmel. (xliii, T). 



b. Operculum purpu7'oid. 



* Varices three. 



CEROSTOMA, Conrad. Yarices wing-like ; aperture usually den- 

 tate within the outer lip, with a produced tooth near its base. 

 Analogous with Pteronotus. It is very diflftcult to define the 

 boundary between this group and Pteronotus, inasmuch as the 

 operculum of several of the species is not known ; moreover, 

 the labral tooth does not always appear even in those species 

 having a purpuroid operculum. All the species with more than 

 one inter-variceal node appear to be true Pteronoti, and the dis- 

 tribution of the group is mainly Indo-Pacific ; Cerostoma, on 

 the other hand, is North Pacific in distribution, extending from 

 Japau northwards to Behring's Straits, and on the opposite 

 American coast south to Central America. M. Nuttallii, Conr. 

 (xliii, 8). 



* * Varices numerous. 



viTULARiA, Swainson. Shell oblong ; spire short ; body-whorl 



