IIG On the Dentition of Prohoscidiferous Gasteropoda. 



advanced for sncli a proceeding*. The tongue of Clavella dis- 

 torta is unequivocally Buccinoid, and tlie shell is now even 

 taken as tlie tjpe of the genus Triumphis. It is quite gratui- 

 tous to say that Fiisiis hngcevus of Solander and Cyrtulus 

 serotinus of Hind are members of the same genus. It may be 

 very pleasant to discover a living species of a genus fossil as 

 far back as the Eocene period ; but where is the proof of such 

 a position ? The naming-difficulty is nowhere more remark- 

 ably illustrated than in the members of this family, for which 

 I have chosen the name Cyrtulidcc, 



FdscioJaria (PI. XIII. fig. 6) and Mitra (fig. 7) form the types 

 of two distinct families : the former, with its lengthy ribbon 

 and narrow median series, differs remarkably from the latter, 

 in which the odontophore is short and broad ; moreover the 

 shell-characters are suflficiently distinctive. 



Conchologists in general assume that Turhinellus and Cyno- 

 donta belong to the same family ; but the proof of this has 

 never been made plain. Cynodonta (fig. 8) alone appears to 

 have imdergone examination ; and a family is certainly re- 

 qiiired for its reception, as it is not conformable with any 

 other already established. 



In Harpa the propodium is largely developed ; but it is 

 simple or without the median fissure above which characterizes 

 all the Olivida^ proper. The head and tentacula are remark- 

 ably small as compared with the great mass of the foot. The 

 proboscis is in keeping with the head and very small, and the 

 odontophore is so minute as to be readily overlooked by inex- 

 perienced observers. 



The lateral plates are quadrilateral, bearing a broad tri- 

 angular tooth ; but both are so delicate and rudimentary as to 

 require a nice adjustment of the light to render them visible 

 at all. The central plates are also quadrilateral, but concave 

 in front and convex behind, bearing a large conical tooth in 

 the middle, with a very small one on either side, near its base. 

 It would appear that the diminutive size of the whole ribbon, 

 or the rudimentary nature of one or more of its elements, anti- 

 cipates as it were some decided change in the plan of the 

 dentition of the next succeeding family. Thus the rudimentary 

 pleural teeth of TIarpa indicate the alHance of that genus with 

 some other in which those teeth arc more highly developed ; 

 and in keeping with this reasoning, if no pleural teeth are at 

 all present in the Volutidai and Marginellidw, we cannot affirm 

 on this ground alone that their lingual dentition is typically 

 uniserial. 



* 'J'lu' youn,u- Ci/ii((la!< is a voiitabli' T.rtuiai'clcuiu Fiisux. 



