GASTEROPODA gcCTIBllANCIIlATA. 



STROM ATI A, Lam. 



The shell moiv hollow, the spin- 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 thin that of the Halyotidos*. 



In tin- following genera, which are separated from the Patellae, the 

 shell is perfectly symmetrical, as well as the position of the heart and 

 bram-hia- f. 1" tin- 



Fissi 1:1:1.1. \, Lam., 



\\V perceive a broad fleshy disk under the belly, as in the Patella?, 

 a conical shell placed on the middle of the back, but not alw:i\ - 

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

 fice, which all'ords at once an issue to the firces and a passage to the 

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

 of the branchitr, 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- 

 inentsj. 



EMAKGINULA, Lam. 



'1'h i' structure of the Emarginulse is similar to that of a Fissurella, 

 except that instead of the hole in the summit, there is a small cleft 

 or emargination in the anterior margin of their mantle and shell, 

 which also penetrates to the branchial cavity ; the margin of the mantle 

 envelopes and covers a great part of that of the shell ; the eyes are 

 placed on a tubercle of the external base of the conical tentacula, and 

 the margin of the foot is furnishes with a range of filaments . 



P.\ ii. \ropiicmus, Lam. 



A great portion of the shell curved by the reflected margin of the 

 mantle, as in the Emargiuujae ; the shell itself oblong, slightly conical, 

 and without hole or emargination ; the branchiae and other organs, as 

 in the preceding general). 



///i* imitrrfnraia, Gm., Chcmn., X, clxvi, 1600, 1601. 



f They art! tin- I'ARACKPHALORA CKR VI CO-BRANCH I.K BRANCHIFKRA, 



J All the Patella? of the fifth division of Gtnelin, except Pat . Jissura ; among others, 

 /'.</. </i-,rr,i, I.M.. .VJ7. i. 2 ; /'. nimbusa, List., 528,4. We have a species in 

 u In.-h tlu >h< 11, at least six times the size of the mantle, simply surrounds the hole 

 of the summit like a rintr, Fusurtlln unnulafu, Cuv. 



Patella fiswra, L. f List., 543, 28, &c. The PALMARIA, Montf., most he 

 allied to this 1:1 ; 



II Patella amlriyu*, Chemn., C \( II, 1918. 



.VII. Funtrelltt, Emarginul<r, and Parmuphori are also found fossil. 



