MOLLUSCA. 493 



Haliotis, 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 Sto- 

 matia, 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 

 filaments. The shell is placed on the back with the spiral 

 part behind, and the row of holes on the left side, through 

 which some of the filaments are protruded. The animal is 

 attached to the shell by a single large muscle. The entry 

 to the branchial cavity, which likewise contains the termi- 

 nation of the rectum and oviduct, is on the back. The 

 gills are in two ridges, consisting of complicated branched 

 filaments. At the entrance of the cavity, the cloak is fur- 

 nished with a slit, the left margin of which rests upon the 

 pillar of the shell. The edges of this sht are furnished with 

 filaments, which pass through the anterior holes of the shell. 

 The use of this singular arrangement is unknown. The 

 branchial cavity likewise contains the viscous organ, in com- 

 mon with the Pectinibranchiae. 



The hood is emarginate, with a long tentaculum on each 

 side, behind which, towards the side, is a cylindrical pro- 

 tuberance, bearing the eye at the top. The mouth is in 

 the form of a short proboscis, with two corneous plates as 

 cheeks, and a long narrow tongue extending backwai'ds, 

 and covered with spines. The pharynx is dilatable, with in- 

 ternal folds. The salivary glands are very small. The gul- 

 let is very short. The stomach is divided into two portions, 

 the first of which is striated longitudinally with a glandular 

 structm-e, and receives a biliary duct. The second is separ- 

 ated from the former by a valve, is smaller, with transverse 

 striae, and a double ridge. It likewise receives bile through 

 two apertures. There is another valve at the pylorus ; and 

 the intestine, after making some turns, is surrounded by 



