REPORT ON THE TUNICATA. 203 



right side ; it is prominent, and distinctly lobcd. It is directed anteriorly and to the 

 right side. The atrial aperture is on the dorsal edge, one-fourth to one-third of the 

 distance from the anterior to the posterior end. It is prominent, is distinctly lobed, and 

 points more or less anteriorly. 



The surface is rather uneven, being seamed by a number of shallow grooves, which 

 have mostly a longitudinal course. The posterior end of the body, which is usually 

 prolonged into a more or less uneven base of attachment, has often irregular rough 

 processes projecting from it. The colour is a dull yellowish-grey, -with occasional darker 

 patches, especially at the place of attachment. 



Length of the body, 17 cm. ; breadth of the body, 5 '5 cm. 



Tlie Test is cartilaginous and moderately thick, but soft and flexible. Vessels arc 

 al mndant. 



Tlie Mantle is strong, and the musculature is well developed on the right side of the 

 body and round the apertures. 



The Branchial Sac is strong, and is slightly plicated longitudinally. The transverse 

 vessels are of two sizes, but these are not arranged with great regularity ; usually several 

 of the smaller size occur between every two of the larger. The internal longitudinal 

 bars are strong and regular, and bear large curved papillae at the points of intersection 

 with the transverse vessels and smaller intermediate ones, which are usually connected by 

 delicate horizontal membranes. The meshes are slightly elongated transversely, ami 

 contain each eight to ten stigmata. Occasionally much narrower transverse vessels are 

 present for short distances, thus forming two rows of small stigmata in a mesh. 



The Dorsal Lamina is a broad membrane, strongly ribbed transversely, and having the 

 edge toothed in some parts and plain in others. 



TJie Tentacles are simple, not long but rather stout, and all of one size. 



Tlie Dorsal Tubercle is large but simple. It lies in a shallow peritubercular area, and 

 extends anteriorly almost to the bases of the tentacles. The shape of the tubercle is 

 ovate, while the aperture is at the narrower anterior end. Both horns are turned to the 

 right. 



This is a large and somewhat variable species, which appears to be common at 

 Kerguelen Island. In the first part of the Preliminary Eeport it was considered as 

 being identical with Ascidia mentula, 0. F. Midler, a species to which it is closely albed. 



The body is elongated, and in the larger specimens is often curved (PI. XXX. fig. 1), 

 while in younger examples it has a much more regular form, and is not so elongated 

 (PI. XXX. fig. 2). In the young individual also the area of attachment at the posterior 

 end is comparatively small, while in the larger specimens it is much produced and irregu- 

 larly twisted, extending in one case more than 7 cm. beyond the posterior end of the 

 body. 



(ZOOL. CHALL. EXP. — PART XVII. — 1882.) E 27 



