ERATO. 7 



genus Ringicula, Deshayes, has also been thought to resemble 

 Marginella in its shell, but this resemblance is a superficial one 

 only, and recent studies of the animal have confirmed its con- 

 chological approximation to Actseon.* 



Synopsis of Genera. 



ERATO, Risso. Shell obovate, polished ; spire short, conical, distinct ; 

 aperture linear ; outer lip without varix, but thickened towards the 

 middle, denticulate within ; columella with distinct plaits at the fore- 

 part. Dentition,f PI. 2, fig. 7. 



Subgenus ERATOPSIS, Hoernes and Auinger. Shell granular-tuberculate, 

 with a longitudinal sulcus on the back of the body- whorl as in Trivia. 



MARGINELLA, Lamarck. Shell ovately oblong to subcylindrical. 

 smooth, polished, sometimes longitudinally ribbed ; spire short, conical 

 or concealed ; aperture narrow, elongated, obtuse or truncated in front ; 

 columella plicate ; outer lip with a thick marginal varix, its inner 

 margin smooth or crenulated. Dentition, PI. 2, figs. 8, 10. 



Subgenus VOLVARIA, Lam. Shell subcylindrical, spire very short or 

 concealed ; outer lip of aperture without varix or thickening. Dentition, 

 PI. 2, fig. 9. 



The type of Volvaria is F. buttoides, Lam., an eocene fossil of France 

 and Belgium (Plate 8, fig. 28). 



(ienus EKATO. Ri>so. 



The few recent species comprised in this group, were approx- 

 imated to Cypraea, Valuta, Columbella and Marginella by 

 ancient authors ; and in proposing their new genus Eratopsis, 

 Messrs. Hoernes and Auinger remark upon the close resemblance 

 of its species to the Trivia, or more properly Pustularia group 

 of Cypraeidae. The only animal of the genus that has been 

 figured is that of the European species E. laevis (PL 4, fig. 40) ; 



* Fischer, Jour, de Conch., 3d ser., xviii, 113 ; Watson, Ibid., 312. 

 



f I figure the dentition of Erato callosa, Ad. and Reeve, the only 

 species which has been examined. It is entirely unlike the normal type 

 of Marginella, and approximates closely to that of Cyprwa. A form of 

 Marginella glabella has, however, been recently discovered to possess 

 lateral teeth (ante p. G . Troschel has made serious mistakes in the identi- 

 fication of species of which he gives the dentition, and it is possible that 

 this is another. It will, [ think, be necessary to have more evidence before 

 allowing the position* of Erato to be determined by the dentition. Con- 

 chologically it is certainly closely allied to Trivia in the Cypneidse 



