Di ASPIDOBRANCHIA. FISSURELLADE. 
The shell shield-shaped or depressed-conic ; its vertex per- 
forated ; its foramen oval or oblong. 
The animal with the head and neck free. The mouth rostri- 
form and retractile without jaws. Two conic tentacles bearing 
the eyes at their external bases. The mantle is dilated late- 
rally, lining the interior margin of the shell, bearing the bran- 
chize underneath, and always projecting beyond the margin of 
the shell. The branchize two, pectinated above and very promi- 
nent from the branchial cavity on each side of the neck. 
The foot is broad and oval. The anus terminates at the middle 
of the base of the neck. The heart is situated laterally above 
the neck. The brain sends round the neck some slender 
branches of nerves anteriorly and posteriorly, and from the in- 
ferior part of the nervous circle descend two branches to the 
viscera and the foot. 
Synopsis Generum. 
Testa patelliformis, vertice perforata.... 97. FissuRELLA. 
Testa conica, elevata, vertice recurvo, ante 
verticem perforata ....0.... 0. 2..2.. 98. Cumommpae 
Genus 97. FissuRELLA. 
Fissurella, Lamarck, Cuvier. 
Testa patelliformis, clypeiformis, aut depresso-conica, subtis 
cava, vertice perforato ; foramine ovato vel oblongo. 
Animal : capite anteriis truncato. Tentacula duo conica ; 
oculis ad basin externam. Os terminale, simplex, maxillis 
nullis. Pes latus, crassissimus. 
The shell limpet-shaped, shield-shaped or depressedly conic, 
hollow below, the apex perforated, the aperture oval or oblong. 
The animal with its head truncated anteriorly, two conic 
tentacula bearing the eyes at their external bases; the mouth 
terminal, simple, without jaws ; the foot broad and very thick. 
1. FissuRELLA GRAECA. 
F. testa ab apice ad basin costata, costis lineis circularibus 
elevatis superficiem cancellatam efficientibus. 
