OF MOLLUSCA. 207 



I. Onchtdoris. 



Body depressed. Mantle large, strengthened with spicula. Dor- 

 sal tentacles laminated. Head veiled, distinct. Oral tentacles none. 

 Gills simply pinnate, set in an open circle, non-retractile. Lingual 

 membrane narrow, with two rows of large, and two of small rudi- 

 mentary ones. 



1. O. Leachii, t. 67. f. 9, 15, t. 214. f. 1, t. 268. f. 7. 



2. O. muricata, t. 67. f. 5. 



3. O. diaphana, t. 217. f. 1. 



4. O. pusilla, t. 217. f. 2. 



5. O. sanguinea, t. 223. f. 5. 



6. O. ?, t. 233. f. 4. 



7. O. sparsa, t. 2/1. f. . 



In Onchidoris Leachii the cloak is armed with moderate-sized 

 spicula. The spawn is cup-shaped, of few coils. The tongue with 

 two large spines and two or more rudimentary ones ; usually a simple 

 central plate. — Alder. 



O. depressa has a very flat body, with large spicula symmetrically 

 arranged. Spawn in many narrow coils. Tongue with two large 

 broad spines and two rudimentary ones ; no central plate. — Alder. 



2. ACANTHODORIS. 



Body convex. Mantle with soft conical tubercles. Dorsal ten- 

 tacles laminated, retractile within marginated cavities ; oral tentacles 

 leaf-shaped, united into a veil. Gills united at the base, non- 

 retractile. Tongue narrow, with two large denticulated spines and 

 six or eight rudimentary ones ; no central plate ; a spinose buccal 

 collar, with rudimentary under-jaw. — Alder. 



1. A. pilosa,t. 67. f. 6, 10. Doris subhevis, t.231.f.9. D.Flemingii, 



t. 67. f. 11. 



2. A. lsevis, t. 69. f. 6, t. 214. f. 6. 



Branchial plumes of Acanthodoris pilosa with a double row on each 

 plume stem of irregularly globular hollow bodies, with elastic walls 

 separating the inner and outer channels of the stem from each other, 

 forming a white star-like centre to the gills. Found from coral- 

 line zone to half-way between low- and high-water mark. — Hancock 

 fy Emb. Phil. Trans. 1852. 



3. VlLLIERSIA. 



" Mantle with a continuous calcareous shield, pierced with holes 

 for the tentacula, gills and vent." — D 'Orb. Teeth ? 



1. V. scutigera, t. 213. f. 1. 



