BRACIIIOPODA. 501 



Order Saccobranchiata. 



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 Botryllidce. 



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

 in which the individuals are grouped into systems. 



Genera Sigillina, Polyclinum, ApUdiiun, Amaroucium, Diazona, 

 Didemnum, Leptoclinum, Botryllus. 



Family Clavellince. 



Body fixed; individuals connected by repent tubular prolongations 

 of their common fused tunics. 

 Genera Clavellbia^ Perophora. 



Family AscidladcB. 



Body fixed : individuals gregarious or isolated. 



Sessile Genera. Ascidia, Cyathia, Dendrodoa. Chelyosoma. 



Pedunculated Genera. Boltenia, Cystinyia^ Bipapillaria, 



Family PelonaiadcB. 



Mantle adhering extensively to tunic, which is usually buried in 

 mud. 



Genus Pelonaia. 



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 £t't the extremity next the outside, the other at that next 

 the inside, of the common cylinder. 



Genus Pyrosoma. 



Order TiEXiOBRANcniATA. 



Mantle adhering throughout to the tunic. Orifices without ten- 

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

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



Genus Salpa. 



Class BRACHIOPOBA. 

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



K K 3 



