MOLLUSCA. 513 



(A). Body sessile. The angles of the branchial meshes 

 furnished with papillae. - The thorax, or cavity containing 

 the branchiae, cylindrical. The abdomen is inferior, with 

 a stalk. Ovarium sessile, and single. 



65. DIAZONA. Body orbicular, with a single system of 

 animals disposed in concentric circles. 



The substance is gelatinous. The ovarium enclosed in 

 the fold of the intestine. D. violacea of SAV. Tab. ii. f. 3. 



66. POLYZONA. Body polymorphous, with many sys- 

 tems disposed subcircularly. 



The body is subcartilaginous. The individuals are dis- 

 posed irregularly around the common centre. SAVIGNY 

 inadvertently termed this genus Distoma, a name long 

 pre-occupied among the Intestina. The Alcyvnium rubrum 

 of Plancus, and the Distomus variolosus of GAERTNER, 

 belong to this genus. The last is a native species. 



(B.) Body pedunculated. 



67. SIGILLINA. Body a solid cone, consisting of a sin- 

 gle system of many individuals, irregularly disposed, one 

 above the other. 



The thorax is short, and hemispherical. The angles of 

 the branchial meshes destitute of papillae. The abdomen 

 is inferior, sessile and larger than the thorax. The single 

 ovarium is pedunculated. S. australis, SAV. Tab. iii. f. 2. 

 brought from New Holland, by M. PBRON, is the only 

 known species. 



b Branchial orifice only furnished with six rays. 



(A). Body pedunculated. System single, circular, and 

 terminal. 



68. SYNOICUM. Anal orifice rayed. 



The body is cylindrical. The anal orifice has six very 

 unequal rays ; the three largest forming the exterior mar- 

 gin of the central star. The stomach is simple. The an- 

 gles of the branchial meshes destitute of papillae. Ovarium 

 VOL. ir. K k 



