PROSOBRANCHIATA. 



789 



The genus has been split up into several sub-genera (Bittium, Tri- 

 foris, Ceritella, &c), but these are of little importance. 



Family 34. Aporrhaid^e. — In this family the shell is fusiform, 

 turreted or conical ; the aperture is prolonged in front into a canal ; 

 the outer lip is expanded, aliform or digitate ; and the operculum is 

 horny. The members of this family are 

 all marine, and they are closely allied to 

 the StrombidcB. The two principal genera 

 in this family are Apo?-rhais itself and 

 A/aria. 



In Aporrhais (fig. 694) the shell is 

 spindle-shaped, with a turreted spire, and 

 the outer lip of the adult is greatly ex- 

 panded and lobed, the inner lip being 

 callous. The aperture is narrow, and is 

 prolonged into a longer or shorter anterior 

 canal, while its posterior angle is prolonged 

 into an open tube, and the outer lip is 

 sinuated in front. The genus has been 

 broken up into numerous minor groups, 

 and is represented by numerous Jurassic, 

 Cretaceous, and Tertiary forms, and by a 

 few recent species. The genus Ala?'ia 

 comprises forms with a general resem- 

 blance to Apo?-f]iais ; but there is no 

 posterior canal, and the outer lip has no 



proper sinus in front. The species of Alaria, in the wide sense of 

 the name, are confined to the Jurassic and Cretaceous deposits, 

 being especially abundant in the former. 



Family 35. Strombilve. — In this family the shell is conical or 

 fusiform, with a pointed spire. The aperture is prolonged into a 

 canal in front ; and the outer lip is expanded, and has a notch or 

 sinus in front, near the canal. The operculum is horny and claw- 

 shaped. The foot is narrow and adapted for leaping, and there is 

 a long proboscis, with two tentacles carrying the eyes at their apices. 

 The members of this family are all marine. 



In the genus Strombus the shell has a short spire and a large 

 body-whorl, and the long aperture is prolonged into a short canal 

 in front and has a notch behind. The outer lip is expanded, and 

 is more or less deeply indented or notched in front, near the canal. 

 The genus is represented by a number of recent species, and by a 

 moderate number of Cretaceous and Tertiary species. 



The genus Pteroceras (or Pterocera) comprises the so - called 

 "Scorpion-shells," in which the shell of the adult (fig. 695) has its 

 outer lip furnished with long claws, one of which forms a posterior 



694 



Cretaceou 



Starkie Gardner.) 



Aporrhais Parkin- 

 (After J. 



