of mollusca. 213 



4. Ancula. 



Head produced at the sides into tentacular processes. Body elon- 

 gate, slug-like, smooth ; forehead simple, without any veil. Mantle 

 obsolete, forming a semicircular ridge of simple or clavate beards, 

 surrounding the plumose non-retractile gills, round the vent. Ten- 

 tacles two, clavate, laminated, with filiform non-retractile styliform 

 appendages on the base. Lingual membrane with four series of 

 spines, the two next the medial line large and broad, with the inner 

 edge denticulated ; no central spine ; buccal collar spinose. 



1. A. cristata, t. 204. f. 4, t. 222. f. 2 ; Forbes fy Hartley, B.M. 

 t. . f . . 



b. Lingual membrane narrow, with twelve or sixteen series of teeth 



(p. 211). 



Fam. IV. POLYCERAD.E. 



Body limaciform, smooth. Mantle obsolete. Tentacles two, la- 

 minated, retractile or non- retractile. Gills non-retractile, with lateral 

 appendages. Lingual membrane rather narrow, with twelve to six- 

 teen series of teeth, two next to the centre on each side large ; no 

 central series. Jaws lateral, corneous. 



* Tentacles non-retractile. 



1. POLYCERA. 



Mantle indistinct, forming a dilated veil, bearing tentacular fila- 

 ments, and a ridge bearing a row of tubercles on each side of the 

 back ; branchial plumes simply pinnate, with a linear branchial ap- 

 pendage on each side. Frontal appendage simple. 



1. P. quadrilineata, t. 64. f. 3, t. 223. f. 1. Var. 1. t. 204. f. 1. 



Var. 2. t. 204. f. 3, t. 205. f. 5 ; Forbes $• Hanley, B.M. t. Y.Y. 

 f. 5. 



2. P. lineata, t. 232. f. 3. 



3. P. typica, t. 204. f. 2. 



4. P. cornuta, t. 64. f. 1. 



5. P. ornata, t. 204. f. 8. 



6. P. citrina, t. 204. f. 6 = P.Lessonii, D'Orb.Mag.Zool.xii.t. 105 ; 



Alder $• Hancock, Monog. t. 24 = P. modesta, Loven. 



2. Palio. 



Mantle indistinct, forming a short bilobate veil, tuberculated on 

 the edge, and a ridge bearing a row of tubercles on each side of the 

 back ; branchial plumes branched, with more than one tubercular 

 branchial appendage on each side. 



1. P. ocellata, t. 227. f. 2. 



