REPORT ON THE TTJNICATA. 137 



The Dorml Lamina is represented by a series of closely placed, stout, tapering, 

 languets. 



Tie Tentacles are branched; they are twenty in number, ten large and ten small, 

 placed alternately. 



TJie Dorsal Tubercle is rather large ; it is elliptical in outline, and is placed with its 

 transverse axis directed anteriorly and posteriorly, the opening being at the right .side ; 

 both horns are turned in and form moderately large spirals. 



This is a very striking species, and although an ordinary Cynthia in its structure, is 

 quite unlike any other species in external appearance (PI. XV. fig. 5). The anterior 

 end is large and rounded and bears the two apertures, while the posterior is prolonged 

 backwards into a short stalk by which the body is fixed. The entire surface is raised 

 into convolutions which, taken along with the yellowish white colour, suggested the 

 specific name cerebriformis. The apertures lie upon the right side, which is concave, 

 while the left is strongly convex. It looks as if the anterior end, bearing both apertures, 

 had been forcibly bent over, so as to form the front of the right side. The openings are 

 very distinct (PL XV. fig. 5), and each is surrounded by four prominent lobes. 



The branchial sac (PL XV. fig. 6) is that of a typical Cynthia. The folds are large, 

 and have each a number of internal longitudinal bars, which are closely crowded at the 

 crest of the fold. The transverse vessels are all of one size and are rather strong. The 

 meshes are slightly elongated transversely, and are usually not divided ; they contain 

 from five to seven stigmata each. 



The dorsal tubercle is large, and lies in rather a shallow peritubercular area (PL XV. 

 fig. 7). The opening between the spirals is directed to the right side ; each spiral is 

 composed of about two turns, but the anterior is considerably the larger one. 



The oesophageal aperture lies very far forwards in the branchial sac, and there is no 

 distinct stomach. The digestive tube runs first posteriorly and then ventrally in irregular 

 curves, so as to reach the ventral edge of the body, where it turns sharply round pos- 

 teriorly, and then sweeps round the lower end of the body and turns anteriorly at the 

 dorsal edge so as to reach the neighbourhood of the atrial aperture. The general course 

 is similar to that found in the genus Corella amongst the Ascidiidse. 



One specimen of this curious species was obtained at Port Jackson, Australia, June 

 3, 1874 ; depth, 30 to 35 fathoms ; bottom, rock. 



Cynthia fissa, Herdman (PL XV. figs. 8-11). 



Cynthia fissa, Herdman, Prelim. Rep., Proc. Roy. Soc. Edin., 1880-81, p. 58. 



External Appearance. — The shape is ovate, with a deep cleft at the anterior end of the 

 dorsal edge extending nearly half way through the body ; it is slightly flattened laterally, 

 and is attached by the posterior end and nearly the posterior half of the left side. The 



