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 

 branchiae, 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. 



1st Tribe. 



Shell ear-shaped, flat, with a lateral, and nearly concealed 

 spire. 



Family Haliotidce. The genera of this group exhibit well- 

 marked characters in the shell. In the Haliotis, the left mai - 

 gin of the shell is pierced by a row of holes. In Padola these 

 holes are nearly obliterated ; but there is an 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- 



