REPORT ON THE TUNIOATA OF PLYMOUTH. 61 



Further the lamina of Sliiiteria rubricollis is described as being on- 

 rolled, the concavity being to the right ; my figure also shows that 

 the marginal languettes of P. Listeri are bent over in a precisely 

 similar way. 



In Ecteinascidia turhinata (Herdman) and diaphanis (Sluiter) the 

 dorsal lamina is represented by tentacular languettes unconnected by 

 a longitudinal membrane. This membrane is present in E. Thurstoni 

 (Herdman), while horizontal membranes are quite absent, and with 

 them also every trace of interserial ridges on the sides of the dorsal 

 lamina. In E. Moorei (Herdman) all the horizontal structures are 

 well developed, but the longitudinal lamina is absent. 



Family 3.— DIAZONID^. 



Body large, consisting of a thorax and abdomen connected by a 

 slender, more or less elongate oesophageal region ; stolouial tubes 

 arising from the posterior end of the abdomen. 



Test gelatinous or semi-cartilaginous, greatly developed around 

 the basal stolonial tubes, with formation of a thick common test, in 

 which the abdominal portions or the entire bodies of the zooids are 

 imbedded ; apertures terminal, each divided into six lobes, rarely 

 smooth. 



Musculature consisting of both longitudinal and transverse fibres, 

 which for the most part anastomose freely ; longitudinal fibres espe- 

 cially well developed. 



Branchial sac large ; with or without festooned horizontal mem- 

 branes ; interserial papillae always present, supporting complete or 

 rudimentary internal longitudinal bars ; longitudinal bars not papil- 

 late ; dorsal lamina represented by a series of languettes with long- 

 tapering ends ; dorsal tubercle a large, longitudinally ovate slit 

 surrounded by broad raised margins ; branchial sac not folded. 



Heart recurved upon itself.'^ 



Genitalia in the loop of the intestine, or extending considerably 

 behind it ', oviduct present or absent. 



Re2:)roduction by gemmation as well as from ova, with formation 

 of colonies of great size ; colonies without systems. 



This family, including the genera Diazona (Savigny) and Tylobran- 

 chion (Herdman), has relations both with the Cionidae, Distomidae, 

 and Polyclinidae. To Lahille belongs, I believe, the credit of first 

 emphasizing the resemblances between Diazona and Tylohranchion, 

 the latter being one of the most interesting of the " Challenger " 

 forms made known to us by Professor Herdman's researches. As 



* This has not yet been estalilished for Tylohranchion, but is probably tbe case. 



