GASTEROPODA. 13 



it as sufficiently elonf?ated. Fig. 15 is the representation of a shorter and more 

 inflated variety, which might perhaps be considered as a species, with the name of 

 intcrmedius, except that C. myosotis has in itself a tendency to extraordinary variation, 

 and coming from a formation in which we are presented in other species with so 

 many monstrous forms, we may be allowed, if necessary, a more than common 

 deviation in this case. The number of teeth upon the columella being three, with a 

 slio-ht difference in their size and inclination, at one time induced a belief that it might 

 be distinct, but the recent species, possessing even a greater degree of variation, will 

 justify this being considered only as a variety. One specimen from the cabinet of 

 Capt. Alexander, and one of my own, are all that I have seen from the Mammaliferous 

 Crag. 



Ord. PECTINIBRJNCHIJTA, Cuv. 



Sect. a. SOLENOSTOMATA, Fleji. 

 Gen. OvuLA,* Bmgidere, 1792. 



Amphiceras. Gronov. 1781 (fide Gray). 

 OVBLTJS. Be Montfort. 1810. 

 SiMNiA. Lmch. 1819. Rlsso. 1826. 

 OvuLUM. G.B.Sowerhy, 18— (?) 

 Bulla (spec.) Linn. 

 Calpurna. Flem. 1828. 

 BiROSTRA. Swaitis. 1840. 



Gen. Char. Shell fusiform or oviform, sometimes attenuated or greatly extended 

 at each extremity ; externally smooth or very finely striated ; convolute upon a nearly 

 horizontal axis, with a hidden spire ; aperture elongate and narrow ; outer lip 

 generally inflected and denticulated ; inner lip smooth. 



In form and mode of volution this genus approaches some of the species in the genus 

 Bulla, especially BuUa acuminata ; but it may be distinguished from that genus by 

 its having both extremities of the aperture canaliculated. In this a fold or tooth- 

 like projection is visible at the upper part above the spire, whereas in Bulla, the fold, 

 when visible, is upon the columella. The surface of the shell, when it has attained its 

 full size, is covered with an enamel-like coat, which is the extension of the columella 

 lip ; and it is therefore supposed that the animal has a mantle so extensive as to be 

 able to envelope the entire shell. It difl'ers from CjqDrsea principally in the ventricose 

 smooth body of the volution, and in the absence of denticulations on the columellar 

 lip. 



In a recent state the greater number of known species are natives of a warm 

 climate, and one is quoted as an inhabitant of the British seas. It is not as yet known 

 below the tertiary formations, and two British fossil species have been published, one 

 of which is from the Crao:. 



■'»• 



Etym. The diminutive of ovum, an egg. 



