REPORT ON THE TUNICATA. 187 



The Test is between membranous and gelatinous in consistency ; it is thin and semi- 

 transparent. 



The Mantle is very thin, and the musculature is slight. It extends for a short 

 distance into the upper end of the long peduncle. 



The Branchial Sac is extremely delicate and filmy ; all the vessels are very narrow. 

 The transverse vessels are all of about the same size, and are connected by longitudinal 

 ducts, so as to form square meshes, in which the secondary or interstigmatic vessels are 

 coiled spirally, as in Corella ; each spiral has about three turns. Internal longitudinal 

 bars are present, but are not papillated ; they are borne on long triangular connecting 

 ducts. 



T/ie Dorsal Lamina is represented by long triangular languets. 



The Tentacles are filiform, and are very long and thin ; they are numerous, arranged 

 rather closely, and are of two sizes, placed alternately larger and smaller. 



Tlie Dorsal Tubercle is irregularly oval in outbne. The aperture is anterior and 

 narrow, and the horns almost meet. 



Tlie Viscera are relatively of small size, compact, and form a narrow band running 

 antero-posteriorly along the dorsal edge of the branchial sac. 



This remarkable form seems to be a deep-sea representative of Corella, and is also 

 allied to Ascidia and Paclujchlcena through Abyssascidia. It is, however, quite distinct 

 from any of these genera. 



The dimensions given above are those of the specimen from Station 299. Of the two 

 others, from Station 146, the perfect specimen is smaller, whde the injured one was 

 apparently much larger. Their dimensions are as follows : — 



A. B. 



Length of the hody, about 5 cm. about 8 cm. 



Greatest breadth of the body, about 2 -5 cm. about 5 cm. 



Breadth of the body at posterior end, 0"8 cm. 



Length of the stalk, 5 cm. stalk absent. 



The shape is remarkable. It is the only known stalked form among the Ascicliidas, 

 and is much more like an abnormal Molgulid. The body is pear-shaped, the ventral 

 and posterior sides being pulled out so as to form a long tapering process, which becomes 

 continuous with the stalk (PL XXV. fig. 1). The apertures are situated at the two 

 extremities of the anterior end, and are wide and tubular, but devoid of lobes. 



The stalk is smooth and glistening, it is rather tougher looking than the rest of the 

 test, and widens as it recedes from the body to its point of attachment to a manganese 

 nodule (PI. XXV. fig. 1). The upper narrow part of the stalk is twisted in one of the 

 specimens. 



The mantle is thin and membranous, with only a few distant muscle bands radiating 



(ZOOL. CHALL. EXP. — PART XVII. — 1882.) R 25 



