GASTEROPOD^V TECTIBRANCUIATA. 353 



the sides of the moiuli. Their branchirc are tentaculiform processes or papillae disposed along the sides, 

 overlying like scales, [or held erect]. They inhahit all seas. 



riie CavoUna, Brugaii^re, have the habit of Kolidiu, bat their brancliire are disposed in rows across the back. 



Tlie Flabellines, Cuv., still exhibit the tentacula of the preceding' genera, witli braiicliije composed of radiating 

 lilamcnts supported on five or six pedicles on each side. They approximfite the Glaucus; and in g-eneral it is to be 

 remarked, that ali the Nudibrancliiata witli liranchiie placed upon the sides of the back are nearly affined. 



The Tergipes, Cuv., 

 Arc ill shape like the Eolidia, l)ut liave only two tentacula, and along each side of the hack there is a row 

 of cylindrical branchirc, each terminated hy a little sucker, which enables tliem to be used as feet : hence 

 the creature can walk in a reversed posture. [This singular structure of the hranchia;, and their pedes- 

 trious use, requires to be confirnied.] The known species are very small. 



The Lvsiri.s, Risso, is known Ijy its oblong body, convex back, two I'diform tentacula, and behind 

 them, upon the neck, two plumose brancluEE. 



The Plocohranchus, Van Hasselt, has two tentacula, and two laliial loljes, and the whole back, 

 widened at the sides, covered with numerous radiating striae, which are the branchiae. In their natural 

 conditions, the widened margins of the cloak are raised, and overlap each other so as to form a covering 

 to the brauchiie, which are thus placed in a sort of cylindrical sheath. The only species yet known is 

 fron; the shores of Java. 



THE THIRD ORDER OF THE GASTEROPODES. 



THE INFEllOBRAXCHIATA. 



These have nearly the habit and organization of Doris and Trifoiiia, but their branehisej 

 instead of being situated upon the back, are on the sides of the body, under the projecting 

 margin of the cloak, where they form two long series of leaflets. [The species are strictly 

 littoral, being gasteropodous and incapable of swimming.] 



The Piiyllidia, Cuv. 

 Their naked, and generally coriaceous cloak, is not protected 1jy any shell. Their mouth is a small 

 proboscis, and has a tentaculum at each side ; two other tentacula protrude above from two little 

 cavities of the cloak. The anus is in the liinder part of the cloak, and the oriiices of generation under 

 the right side in front. The iieart is ahi)ut the centre of the back ; the stomach is simple, membranous; 

 and the intestine short. There are several species in the Indian ocean. 



Thl; DinivLLiDES, Cuv. — 

 Have branclii;e nearly similar to those of Phyllidia, hut the cloak is more pointed liehind ; the head, of 

 a semicircular figure, has a pointed tentaculuin on each side, and a slight tubercle : the anus is on the 

 right side. 



[The Anci/Ziix, Geofl'roy,— a fresh-water Gasteropode, with a shell similar to that of a Patella, is placed by Rang 

 in this order. He asserts that the animal is branchiferoas, while the Rev. Mr. Berkeley has asserted that it is pul- 

 inonated. They live in stag;nant waters and in rivulets, adhering to stones and aquatic plants.] 



THE FOURTH ORDER OF THE GASTEROPODES. 



THE TECTIBRAXCHIATA.* 



T!iev have their brauchia; attached along the right side, or upon the back, in the form of 

 move or less divided, but not sunmetrical, leaflets; these are more or less covered bv the 

 mantle, m ivhieh a siiiall shell js geiiei ally contained. They approximate the Pectinibranchiata 



