76 WALTEE GARSTANG, M.A. 



Colony gelatinous, sessile ; the zooids superior, their thoracic 

 portions freely projecting. 



Musculature with longitudinal fibres united into well marked bundles. 



Branchial sac with festooned horizontal membranes, supporting 

 complete, rarely incomplete, internal longitudinal bars, not papillate at 

 the point of junction ; dorsal languettes triangular, compressed from 

 before backwards. 



Genitalia in the loop of the intestine ; oviduct (always ?) and vas 

 deferens present. 



In 1853 Professors Forbes and Goodsir announced the discovery 

 of a composite Tunicate allied to Savigny's Diazona violacea, but 

 differing from it in the possession of the following characters : Plain 

 undivided orifices, non-pedunculated abdomen, meshes with "one 

 ciliated opening " only, and apple-green colour. Their genus Syntethys 

 was established upon these grounds, but Alder subsequently wrote to 

 show the generic identity of the two forms, basing his criticisms upon 

 an examination of specimens dredged near Guernsey and possibly upon 

 a re-examination of a portion of one of the original specimens of 

 Forbes and Goodsir. Alder satisfactorily showed that the difference 

 of colour was one due entirely to the action of the spirit used in 

 preservation, and also that the pedunculation of the abdomen is very 

 variable in its extent. He also noted that, after preservation, the 

 division of the apertures into lobes was generally difficult to make out. 

 His conclusion in regard to the generic identity of Diazona violacea 

 and the so-called Syntethys is probably correct, although, as I shall 

 endeavour to show below, his identification of the Guernsey species 

 with that of Forbes and Goodsir from the Hebrides is extremely 

 doubtful. 



4. Diazona violacea, Savigny. (PI. II., figs. 7, 8.) 



Diazona violacea, Savigny. Memoires, pp. 35 — 38, 175, 176, pi. xii. 



— — Fleming. Moll. Animals, 1837, p. 211. 



— meditebbanea, Dujardin. L. c, pp. 499, 500. 



— hebridica, Aldei-. L. c, p. 169. 



— violacea, Cams. L. c, pp. 480, 481. 



