GASTEROPODA PECTINIBRANCHIATA. 371 



ing from one extremity to the other; but the shell, which is protu- 

 berant in the middle, and almost equally narrov/ed at both ends, 

 forms an oval, and the aperture in the adult animal is transversely 

 wrinkled on each side. The mantle is sufficiently ample to fold 

 over and envelope the shell, which at a certain age it covers with a 

 layer of another colour, so that this difference, added to the form 

 acquired by the aperture, may easily cause the adult to be taken for 

 another species. The animal has moderate tentacula, with the 

 eyes at their external base, and a thin foot without an operculum. 



The colours of these shells, also, are extremely beautiful; they are 

 extremely common in cabinets, though with very few exceptions 

 they all inhabit the seas of tropical countries(l). In the 



OvuLA, Brug. 



The shell is oval, and the aperture narrow and long, as in Cyp3«a, 

 but without plicse on the side next to the columella; the spire is con- 

 cealed, and the two ends of the aperture' equally emarginated, or 

 equally prolonged in a canal. Linnaeus confounded them with the 

 Bullae, from which Brugieres has very properly separated them. 

 The animal has a broad foot, an extended mantle which partly folds 

 over the shell, a moderate and obtuse snout, and two long tentacula, 

 on which, at about the third of their length, are the eyes. 



Montfort particularly designates, by the term Ovul^e, those in 

 which the external margin is transversely sulcated(2). 



Those in which the two extremities of the aperture are prolonged 

 into a canal, and in which the external margin is not sulcated, he 

 calls Navettes Volv7e(3). 



When this external margin is not sulcated, ijor the extremities of 

 the aperture prolonged, he styles them Calpurn^(4). 



TerebelluMj Lam. 



An oblong shell, with a narrow aperture, without plicse or v/rinkles, 



(1) For the species see the g-enus Cyprsca, Gmel., and the figures collected by 

 Bvugieres for the Encyclop., tlie Gen. of Shells of Sowerby, No. XVII, and par- 

 ticularly a Monograph by M. Gray, published in the Zool. Journal, Nos. 2, .3, 

 and 4. 



(2) Bulla ovum, L., List., 711, 65, Encyclop., 358, 1. 



(3) Bulla voha, L., List., 711, 63, Encycl., 357, 3; — B. birostris, Encycl.,S57 

 1; Sowerb., lb. 



4) Bulla verrucosa, L., List., 712, 67, Encyc, 357, 5, from which we do not 

 separate the Ui.tim;e, Montf. : or Bulla gibhosa, L., List., 711, 64, Encyc. 357, 4. 



