386 MOLLUSC A. 



observe three or four filaments which the animal can protrude through 

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



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

 holes are nearly obliterated, and there is a deep sulcus that follows 

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

 Padole briquete, 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- 

 tellfP, the shell is perfectly syinnietrical, as well as the posi- 

 tion of the heart and branchiai(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., except the imperforata and t\\e perversa. 



This genus, although it has been denied, most certainly has its counterpart 

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

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

 xlv, f. A. 



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



(3) They are the PAnACEPHAioRA CEnyico-BRANCiti^ Branciiifera, Blainv. 



(4) All the Patellas of the fifth division of Gmelin, except Pat. fissura.- among 

 others, Pat. grseca. List., 527, 1, 2; — P. nimhosa. 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 the summit like a ring, — Pissurella annulata, Cuv. 



