DIAZONA HEBRIDICA. 161 



slender and situated a little to one side. Mantle 

 muscular, highly contractile. Branchial sac with 

 numerous rows of oblong meshes, the intersections 

 with large papilla?. Oral lamina with long filaments, 

 broad at the base and triangular. Abdomen reddish, 

 enveloped in the general mass. 



Lenrjtli of individuals about two inches. Common 

 mass sometimes six inches in diameter. 



Hab. 'Deep water. 



ENGLAND. --The Ascidian got by Mr. Couch from 

 deep water on the Cornish coast, and exhibited at the 

 meeting of the British Association at Plymouth [1841] 

 probably belongs to this species. 



SCOTLAND. Close to Croulin Island, near Applecross, 

 Ross, dredged in 30 fathoms water (Me Andrew}. 



CHANNEL ISLANDS. Guernsey (Alder ; Norman). 



First record. Forbes & Goodsir, 1850; coll. 

 McAndrew. 



That the Syntethys hrlrtrfirus of Forbes and Goodsir 

 is really a Diazona, will, we think, be obvious to any 

 one who has the opportunity of carefully investigating 

 its characters, one or two of which appear to have 

 escaped the observation of those distinguished natu- 

 ralists who first described it. The division of the 

 apertures into six lobes is very difficult to make out, 

 except in well-preserved specimens, and the elongated 

 and pedunculated form of the abdomen is a character 

 varying exceedingly according to the degree of con- 

 traction in which the animal is seen. 



Mr. Alder was so fortunate as to dredge large masses 

 of this remarkable Ascidian at Guernsey in 1853, and 

 had the opportunity of examining it in a living state, 

 when it was at once recognized as the Si/ntethys hebri- 

 dicus of Forbes and Goodsir ; but on placing specimens 

 in spirits the pale apple-green colour of the living 

 animals (PI. XLIX, fig. 5) began to change into a 

 delicate violet, and the whole put on the appearance 

 of the Diazona violacea of Savigny. This author, 



n 11 



