oxciiidorididjE. 57 



Genus CASELLA, H. and A. Adams. 



Body elongated, compressed. Tentacles clavate, sheathed, 

 retractile. Mantle with the margins forming erect, lohate, 

 undulated crests along the sides of the back ; gills composed 

 of six lobes, arranged around the anal orifice. Foot linear. 



Ex. C. Gouldii, H. and A. Adams, pi. C3, fig. 5. 



In general aspect this genus resembles Scylhca, but the 

 possession of gills surrounding the vent places it with the 

 Dorididw ; the lateral processes of the mantle resemble 

 Lomanotus among the JEolididie. The specimen on which 

 this genus is founded was collected by Mr. Gould in 

 Australia, and is dedicated to that eminent Ornithologist. 



Genus PELAGELLA, Gray. 



Body smooth. Tentacles clavate, non-retractile. Mantle 

 forming a simple, raised edge round the tentacles and bran- 

 chial region ; gills plumose, surrounding the vent. 



Ex. P. Paretii, Veramj, pi. 63, fig. 6. 



In Pehiffella the mantle appears to be reduced to a simple 

 elevated margin, and the branchiae form a beautiful star 

 with simple pinnate rays ; the tentacles are clavate, non- 

 retractile, and pinnate. One species is known, from the 

 Mediterranean. 



Fam. ONCHIDORIDriLE. 



Teeth, two in each cross series. Mantle simple, extending 

 beyond the foot. Gills on the middle of the hinder part of the 

 back, in separate cavities surrounding the vent; vent dorsal. 



In this family the gills are each retractile into its proper 



