Dental PI dies and Teeth of Fivboscnlifh-ous Gastewjwda. 115 



the tnie Pleuvotomes with tlie Olives. Ko dentition can he 

 more characteristic than theirs, or less likely to he confounded 

 Avith any other. The lateral teeth become shorter, more 

 strongly curved, and falcated in a manner peculiar to the 

 family, while the central area only presents a series of un- 

 armed plates. These, however, shadow forth their composite 

 nature by a narrowing in the middle, suggesting their homo- 

 logy with all three central plates of (7/ay«i!»7« blended toge- 

 ther. In Olivella (fig. 12) the corresponding plates are fur- 

 nished with a rov>^ of fine teeth along the posterior border, and 

 the more simple uncini are flanked externally by a single 

 row of thin quadrilateral plates. In Oliva (fig. 13) the uncini 

 are quite simple, without notches or foliations, and closely re- 

 semble their homologues in Turritida^ (fig. 17) and Muricidae 

 (fig. 18). In the Harpida^ (fig. 14), Volutidas (fig. 15), and 

 Marginellida3 (fig. 16) they are altogether suppressed. 



I have placed Clavatula (PI. XIII. fig. 4) by itself as the 

 type of a provisional family until further information is ob- 

 tained by the study of the numerous little shells in this alliance 

 occurring in tropical seas. Much is to be anticipated also 

 from the examination of an equally numerous group referable 

 to the Olive type. 



In the odontophore of Clavatula (fig. 4) we find the most 

 interesting combination of the dentition of Mangelia or Bela 

 (fig. 3) with that of Gyrtidus (fig. 5), explaining to ns certain 

 homological relationships which would be difficult to comjjre- 

 hend without its aid. Thus its fangs may be traced back- 

 wards to Pleurotoina (fig. 10), and thence through the uncinate 

 series to the hooks of Murex or GoncJiolejpas (fig. 18), while its 

 side combs may be followed through the pectinate series to 

 the lateral teeth oi Buccinum (fig. 9), from which it must be 

 apparent that the hooks of Murex and the lateral teeth of 

 Buccimim are not homologous organs, and therefore cannot be 

 convertible. 



Being well aware of the existence of certain fusiform spe- 

 cies having neither plaits nor folds upon the columella of 

 the shell, but with lateral combs in the odontophore, I con- 

 clude that these would form Avith Cyrtulus (Hind) a well- 

 marked family. The Muricoid species, such as Fusus prohos- 

 cidalis, should be carefully excluded, and only the Cyrtuloid 

 members (e. g. Colus rap/zanu-s) retained. My reason for pro- 

 posing the family name Cijrtididce is founded on the study of 

 the anatomy of J\lr. Hind's Cijrtidus serotinus (" Cyrtule du 

 soir " of the French), the type of the genus; and I hold its 

 name to be still intact, though it has been unhesitatingly ab- 

 sorbed into Swainson's ClaveJla, no sufficient data having been 



