GASTEROPODA SCUTIBRANCIIIATA. 
79 
Strom AT iA, Lam. 
The sliell 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* * * § . 
In the following genera, which are separated from the Patellae, the 
shell is perfectly symmetrical, as well as the position of the heart and 
branchiae f . In the 
Fissurella, Lam., 
We perceive a broad fleshy disk under the belly, as in the Patella*, 
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 to the faeces 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 |. 
' Eaiarginula, Lam. 
The 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 §. 
Parmophorus, Lam. 
A great portion of the shell curved by the reflected margin of the 
mantle, as in the Emarginulae ; the shell itself oblong, slightly conical, 
and without hole or emargination ; the branchicC and other organs, as 
in the preceding genera ||. 
* Huhjotis imperforata, Gm., Cbemn., X, clxvi, 1600, 1601. 
-f- They are the Paracephalora Cervico-branchi.e Eranchifera, Blainv. 
t All the Patellae of the fifth division of Gmelin, except Pat.fissura; among others, 
Put. grcEca, List., 527, I, 2; — P. nimbosa, List., 528,4. We have a species in 
which the shell, at least six times the size of the mantle, simply surrounds the hole 
of the summit like a ring, — Fissurella annulafa, Cuv. 
§ Patella fissura, L., List., 543, 28, &c. The Palmaria, Montf., must be 
allied to this genus. 
II Patella amhigua, Chemn., CXCII, 1918. 
Fissurella, Emargimda, and Purmaplwri are also found fossil. 
