72 THE VOYAGE OF H.M.S. CHALLENGER. 



The dorsal lamina (PI. IV. fig. 4, d.l.) is short and broad ; the free edge is cremated, 

 hut a regular series of teeth is not present. 



The tentacles are large and greatly branched, and their branchial surface, from which 

 the pinnae spring, is usually vesicular. The shape of one of the larger tentacles is irregularly 

 pyramidal with the apex generally curled upwards towards the branchial aperture, so that 

 the lovv r er side on which the branches are placed is convex (PI. IV. fig. 4, tn.) The base 

 is very thick, and is seen from sections to be highly muscular. Numerous bundles of 

 fibres, imbedded in the connective tissue and running in all directions and interlacing, 

 occupy a zone extending about half-way to the centre of the tentacle. 



The peritubercular area is very small, and the dorsal tubercle extends across the 

 prsebranchial zone almost to the base of the tentacles (PI. IV. fig. 4). 



The intestine is large and lies on the left side, occupying chiefly the dorsal edge 

 and posterior end. The oesophageal aperture (PI. IV. fig. 4, os.a.) is situated far forward 

 in the sac, generally between one-third and one-fourth of the distance from the anterior 

 to the posterior end. In a specimen 16 cm. in length and 7 '5 cm. in breadth the 

 dimensions of the branchial sac were as follows: — 



From peripharyngeal band to posterior end, ... 8 cm. 



From peripharyngeal band to oesophageal aperture, . . . 2 ,, 



From peripharyngeal band to branchial aperture, . . . 4 „ 



Breadth of sac at level of oesophageal ajierture, . . . 4 ,, 



Breadth of sac at broadest part, . . . . . 6 „ 



The oesophagus is short and wide, and runs directly posteriorly from the oesophageal 

 aperture to open into the large stomach lying on the left dorsal edge of the posterior 

 part of the branchial sac. The intestine issuing from the stomach soon reaches the 

 posterior end of the branchial sac, and after turning towards the ventral edge runs 

 anteriorly for a short distance, then curving dorsally and posteriorly it returns closely 

 pressed against its first part, so that no open loop is formed, and finally runs anteriorly 

 along the dorsal edge of the branchial sac, past the oesophageal aperture, and opens into 

 the relatively small cloaca! part of the peribranchial cavity. 



There are two ovate genital glands imbedded in the mantle, one on each side. That 

 on the left side lies anteriorly to the intestine, and nearer the ventral than the dorsal edge. 

 The glaud on the right side is nearly in the centre, and lies anteriorly and ventrally to the 

 large curved renal sac. 



This species was obtained by the " Nassau " at two localities — Gregory Bay and near 

 Cape Virgins. In the Liverpool Free Public Museum 1 there are some small specimens, 

 which were dredged by Captain W. H. Cawne Warren, off the Patagonian Bank, 

 lat. 41° 30' S., long. 52° 0' W.; depth, 50 fathoms. 



The Challenger specimens (nearly forty) were all dredged at Station 313, January 



1 I am much indebted to Mr. T. J. Moore, the curator of this excellent museum, for his kindness in allowing 

 me to examine specimens of this and several other species of Ascidians in the collection under his care. 



