594 ascidiidjE. 



Genus CHELYOSOMA, Broclerip and Sowerby. 



Body depressed, oolong, fixed, sessile ; test coriaceous, its 

 upper surface consisting of eight somewhat homy, angular 

 plates ; orifices small, prominent, perforating the plaited 

 surface, each surrounded by six triangular valves; gills 

 plicated ; tentacles simple. 



Ex. C. Macleayanum, Broderip and Sowerhy, pi. 133, 

 fig. 5. 



These are curious tortoise-like Ascidians from the 

 shores of Greenland. A single species only has hitherto 

 been discovered. 



Genus BOLTENIA, Savigny. 



Body more or less globular, fixed, pedunculated ; test 

 coriaceous ; orifices lateral, each cleft into four rays ; bran- 

 chial sac longitudinally plicated, surmounted by a circle of 

 compound tentacula. 



Syn. Bipapillaria, Peron. 



Ex. B. reniformis, Mac Leay, pi. 133, fig. 0. 



Sometimes one Boltenia is attached to the stem of 

 another individual. One species, B. reniformis, is an 

 inhabitant of the Arctic seas, living attached to stones in 

 deep water. The sub- genus Cystingia is also found in 

 the Northern seas. 



Species of Boltenia. 



coacta, Gould. pedunculata, Sav. 



micvosoma, Agass. reniformis, Mac Leay. 



ovifera, Linn. rubra, Stirrup. 



