368 MOLLUSCA. 



Calyptr^Aj Lam. 



We observe a conical shell, in the hollow of which is a little lamina 

 that projects inwards, resembling the commencement of a columella, 

 and that interposes itself between a fold of the abdominal sac. The 

 branchiae are composed of a range of numerous filaments, long and 

 slender, like hairs. 



In some of them this lamina adheres to the bottom of the cone, 

 being itself bent into a portion of a cone or of a tube, and descend- 

 ing vertically(l). 



In others it is almost horizontal, and adheres to the sides of the 

 cone, which is marked above by a spiral line that establishes some 

 relation between their shell and that of a Trochus(2). 



SiPHONARiA, Sowerby. 



The shell of the Siphonarise, v/hich have been recently separated 

 from the Patellae, at the first glance seems very similar to a flattened 

 Patella, with radiating sulci; but its margin projects rather more on 

 the right side, and it is excavated beneath by a slight furrow, which 

 terminates at this prominence of the margin, to which there is a 

 corresponding lateral hole in the mantle, for the introduction of 

 water into the branchial cavity, placed on the back, that is closed 

 on every other point. The respiratory organ consists of a few small 

 lamellae, arranged in one transverse line on the roof of that cavityj 

 the tentacula seem to be wanting, the head being merely furnished 

 with a narrow veil(3). 



There are some species, in which even this slight appearance of 

 the canal, in the shell, is effaced, resembling in toto that of a 

 Patella, except in its summit, which is behind(4). In the 



SiGARETUs, Adans. 

 The shell is flattened, its aperture ample and round, and the spire 



(1) Patella equestris, L., List., 54^6 Z2>; Pat. sinensis, lb., 39;Pat.trochi- 

 formis. Martini, I, xiii, 135; Pa^. auricula, Chemn., X, clxviii, 1628 29; Pat. 

 plicata, Nat. Forsch., XVIII, 11,12; Paif. striata, lb., 13. 



(2) Patella contorta, Nat. Forsch., IX, iii, 34, VIII, 11 14; Pa^. depressa, lb., 

 xviii, ii, 11. 



(3) Patella sipho; Siphonovia concinna, Sowerb., Gen. of Shells, No. XXI; ^S*. 

 exigua, Id., lb. See Savigny, Descr. de I'Eg., Zool. Gaster., pi. iii, f. 3, and 

 Coq., pi. i, f. 1. Some years ago M. Gray proposed a genus Gadinia, (Philos. 

 Magaz., April 1824) which is precisely the same as Siphonaria. 



(4) Siphonariatriste?isis, Sow erh., loc. cit. 



