BRACmOrODA. 501 



Order Saccobranciiiata. 



Mantle united to the tunic at the two orifices ; elsewhere com- 

 monly more or less detached. Branchia, a dilated vascular sac, with 

 a tentacular orifice. 



Family BotryUidce. 



Body fixed : tunics of many individuals fused together into a mass, 

 in which the individuals are grouped into systems. 



Genera Sigill'ma, PoIi/cUnum, ApUdium, Amaroucium, Diazona, 

 Didemnum, Leptocliman, Botryllus. 



Family Clavellincr. 



Body fixed ; individuals connected by repent tubular prolongations 

 of their common fused tunics. 

 Genera Clavellina, Perophora. 



Family Ascidiadce. 



Body fixed : individuals gregarious or isolated. 



Sessile Genera. Ascidia, Cyuthia, Dendrodoa. Chelyosoma. 



Pedunculated Genera. Boltenia, Cystingia, Bipapillaria. 



Family Pelonaiadce. 



Mantle adhering extensively to tunic, which is usually buried in 

 mud. 



Genus Pdonaia. 



Family Pyrosomidce. 



Body floating : tunics of many individuals fused into a cylindrical 

 mass, in which they have a verticillate arrangement with two ori- 

 fices, one at the extremity next the outside, the other at that next 

 the inside, of the common cylinder. 



Genus Pyrosoma. 



Order TiENiOBUANcniAXA. 



Mantle adherinsr throu^rhout to the tunic. Orifices without ten- 

 tacles. Branchia ribband-sliaped. Individuals connected, chain- 

 wise, in one generation, solitary in the next : free and floating. 



Genus Salpa. 



Class BRACIIIOPODA. 

 Body symmetrical, with a dorso-ventral biviilvc shell, lined by a 



K K 3 



