96 PTEROTRACHEIDiE. 



nucleus, and a fimbriated dorsal keel ; aperture large, ovate, 

 entire. 



Ex. C. Atlantica, Adams and Reeve, pi. 70, fig. 1. 

 Shell, C. cristata, Linnaeus, fig. 1, a. 



These animals progress very much in the same manner 

 as the Pterotrachece and Firoloidea', darting through the 

 water with great rapidity in a reversed position, their body 

 straightened and their caudal fin undulating from side to 

 side. They appear also to prefer the twilight for the season 

 of their predatory excursions, when they may be taken at 

 the surface, in the trawl, in considerable numbers. They are 

 found in the Atlantic and Pacific Oceans, and in the Medi- 

 terranean, and, like the other Heteropods, are supposed to 

 feed on Acalejjha and other small pelagian animals. 



Species of Carinaria. 



Atlantica, Adams and Reeve. Gaudichaudi, Eyd. 



australis, Quoy and Gaim. gracilis, Reeve. 



cristata, Linn. punctata, D'Orb. 

 depressa, Rang. 



Genus CARDIAPODA, D'Orbigny. 



Tentacles slender, elongate ; eyes distinct, on the sides of 

 the head. Body fusiform, ending in a long, simple, acumi- 

 nate tail ; nucleus pedunculated ; gills pinnate. Ventral fin 

 sub-circular, provided with a sucker. 



Shell minute, cartilaginous, regularly involute ; peristome 

 expanded and bi-lobed in front, enveloping the spire behind. 



Syn. Carinoidea, Eydoux and Souleyet. 



Ex. C. placenta, Eydoux and Souleyet, pi. 70, fig. 2. 

 Shell, 0. placenta, fig. 2, a, 2 } b. 



