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



Length of the body, 5 cm.; breadth of the body, 3 cm. 



Tlie Test is thin, soft, easily torn, and transparent. Vessels are moderately developed ; 

 the main trunks enter on the left side near the base. 



The Mantle is very thin, the muscular bands are delicate, and the course of the 

 alimentary canal is visible from both sides. 



Tlie Branchial Sac is not plicated longitudinally. There are generally five or seven 

 smaller transverse vessels between a pair of larger ones. The internal longitudinal liars 

 are narrow but well marked ; they bear papillae at the angles of the meshes, and smaller, 

 more nearly conical intermediate ones. The meshes are square, and contain each three 

 to five stigmata, generally four. The stigmata are elongate elliptical or oblong in 

 shape, with rounded ends. 



The Dorsal Lamina is rather broad, is delicately and rather distantly ribbed trans- 

 versely and has the edge pectinated ; there are one or two small intermediate teeth 

 between each pair of slightly larger ones — those opposite the ends of the ribs. 



Tlie Tentacles are filiform, they are forty in number, and are of two sizes placed long 

 and short alternately. 



Tlie Dorsal Tubercle is remarkably shallow ; it is basin-shaped, with a wide anterior 

 aperture ; it is pointed posteriorly, and has the horns scarcely turned in. 



This species has the shape of a typical Ascidia, being elongated antero-posteriorly, and 

 attached by the posterior end of the left side (PI. XXXII. fig. 7). 



The dimensions given above are those of the largest specimen, the remaining two being 

 a little smaller, but with much the same proportions. The specimens differ in shape, 

 however, when the test is removed ; one individual having the branchial aperture 

 prominent and placed on a short siphon, while in others it is sessile, and does not project 

 beyond the rounded anterior end. 



The mantle and branchial sac are rather delicate ; in the latter (PL XXXII. fig. 8) 

 two smaller intermediate papillae are occasionally joined by a narrow vessel dividing the 

 mesh transversely ; here and there also the stigmata are only half the normal height, so 

 that a mesh or part of one contains two rows. This condition of the stigmata does not 

 necessarily coexist with the narrow vessel uniting the small papillse, either may be present 

 without the other. Both conditions are shown in figure 8 on PL XXXII. 



The condition of the dorsal tubercle is remarkable (PL XXXII. fig. 10). The dorsal 

 ends of the peripharyngeal bands almost meet before turning posteriorly, so that no peri- 

 tubercular area is formed, and the dorsal tubercle merely lies in the praebranchial zone 

 at the anterior end of the dorsal lamina. It is very shallow, with a wide opening between 

 the horns anteriorly. 



The viscera upon the left side of the branchial sac are not large. The cesojmagus is 

 short, opens into the sac far back, and leads to a comparatively small stomach. The 



