MOLLUSCA+ 183 
situate at the branchial indentation on the left side. The 
_ penis is situate on the right side of the neck; it is external. 
with a crooked, blunt, lateral process near its extremity. 
The mouth is in the form of a short proboscis. The 
tongue is armed with spines, and is long and spirally folded. 
The salivary glands are large. The stomach is membrana- 
ceous, giving off the intestine near the cardia. The intes- 
tine makes two folds. The liver, with the testicle in the 
male, and the ovarium in the female, occupy the posterior 
part of the body, under the spire of the shell. 
2d Subdivision. 
Heart traversed by the rectum. 
This group includes the order Scutibranchia of Cuvier. 
In general form, and in the structure and position of the 
branchiz, the resemblance to the genera of the preceding 
subdivision is very great. The animals differ, however, in 
many particulars. The heart is furnished with two auricles, 
and is perforated by the intestine. The sexes appear to be 
incorporated in the same individual, or rather the male or- 
gans are unknown. The body is protected by a shell, the 
aperture of which is wide, and never closed by a lid. 
Ist Tribe. 
Shell ear-shaped, flat, with a lateral, and nearly concealed 
spire. 
Family Haliotide.— The genera of this greup exhibit well- 
marked characters in the shell. In the Hadvotis, the left mar- 
gin of the shell is pierced by a row of holes. In Padola these 
holes are nearly obliterated; but there isan internal groove and 
external ridge in the line of their direction. In Stomatia, 
there are neither holes nor ridges. In the Halyotis, the 
foot is oval and large. The sides of the body, all round, are 
ornamented with one or more rows of simple or branched fila- 
