MOLLUSCA. PECTINIBRANCHIA. 361 
PECTINIBRANCHIA. 
SCUTIBRANCHIA. 
Heart with two auricles traversed hy the rectum ; sexes incorporated ; 
body covered with a patulous shell; the foot destitute of a lid. 
I. Shell ear-shaped, with a lateral and nearly concealed spire. 
Haliotis. 
(Padola.) 
(Stomatia.) 
II* Shell oblong or conical, simple or subrevolute. 
Ckepidulid^. Cavity of the shell interrupted by a testaceous 
plate. 
a. Marine. 
b. Plate of the cavity spirally decurrent. 
Calvptrsea. 
Infundibulum. 
hb. Plate of the cavity horizontal. 
Crepidula. 
Pileolus. 
aa. Fluviatile. 
Navicella. 
Capulid^. Cavity and margin of the aperture entire. 
Capulus. 
(Carinaria.) 
FissuRELLADiE. Cavity entire ; shell with a perfora- 
tion or slit. 
Fissurella. 
Emarginula. 
Scissurella. 
