386 



MOLLUSCA. 



observe three or four filaments which the animal can protrude through 

 these holes. The mouth is a short proboscis(l). 



The Padoll^, Montf., have an almost circular shell, in which the 

 holes are nearly obliteA'ated, and there is a deep sulcus that follows 

 the middle of the whorls, and is marked externally by a salient ridge; 

 Padole briquets^ Montf., II, p. 114. 



Stromatia, Lam. 



The shell more hollow, the spire more salient, and the holes want- 

 ing? otherwise resembling that of the Halyotides, which it thus con- 

 nects with certain species of Turbo. The animal is much less orna- 

 mented than that of the Halyotides(2). 



In the following genera, which are separated from the Pa- 

 tellse, the shell is perfectly symmetrical, as well as the posi- 

 tion of the heart and branchise(3). In the 



FissuRELLA, Lam., 



We perceive a broad fleshy disk under the belly, as in the Patellae, 

 a conical shell placed on the middle of the back, but not always 

 completely covering it, and perforated at its summit by a small ori- 

 fice, which affords at once an issue for the feces and a passage to 

 the water, required for respiration; this orifice penetrates into the 

 cavity of the branchiae, situated on the fore part of the back, and in 

 the bottom of which terminates the anus? a cavity otherwise widely 

 opened above the head. A branchial comb is symmetrically arranged 

 on each side; the eyes are on the external base of the conical tenta- 

 cula, and the sides of the foot are furnished with a range of fila- 

 ments(4). 



(1) All the Halyotides, Gm., cxc&Tpt \h& imperforata axid. \h& perversa. 



This genus, althoug-h it has been denied, most certainly has its counterpart 

 among the fossils. M. Marcel de Serres has described a species found in the cal- 

 careous strata of Montpellier {Hal. Fhilberti), Ann. des Sc. Nat. tome XII, pi. 

 xlv, f. A. 



(2) Halyotis imperforata, Gm., Chemn., X, clxvi, 1600, 1601. 



(3) They are the Pahacepualoha Cebtico-branchije Hiianciiifera, Blainv. 



(4) All the Patellx of the fifth division ofGmelin, except Pat. fissura,- among 

 others, Pat. grseca. List., 527, 1, 2; P. nimbosa. List., 528, 4. We have a spe- 

 cies in which the shell, at least six times the size of the mantle, simply surrounds 

 the hole of tlie summit like a ring, Flssurella annulata, Cuv. 



