126 SOME ASCIDIAN8 FROM THE ISLD OF WIGHT. 



slightly in position, but it is always nearer the posterior than the 

 anterior end of the body, between half and two thirds of the way 

 down the dorsal edge. Both apertures are small and inconspicuous ; 

 no ocelli were observed in the living animal. 



The dimensions of the largest specimen are as follows : 

 Maximum length . . . • rf ii^ch 



J, breadth . . • f » 



„ thickness . . 'ha 



The test is firm and cartilaginous, though rather thin ; it is not 

 rough to the touch, but its surface is in reality studded with minute 

 tubercles of bluntly conical form. They are so small that they 

 cannot be readily observed when the test is immersed in alcohol, 

 but when removed for a moment from the fluid, the presence of 

 minute projections is detected by the broken reflection of light from 

 its upper surface. A portion of the surface of the test is shown on 

 PL VII, fig. 9, considerably magnified. A series of vertical sec- 

 tions through the test shows that the tubercles are quite solid, and 

 that the culs-de-sac of the test-vessels have no connection with 

 them. The greater part of the test is composed of huge " bladder- 

 cells,^' the largest of which are as large as many of the tubercles 

 on the surface j they are of spherical or polyhedral form. The 

 superficial tubercles are entirely destitute of bladder-cells. 



The body when deprived of the test is at least twice as long as 

 broad in the majority of the specimens, but in one individual the 

 proportion between the two dimensions is slightly less than this. 

 The oral and cloacal siphons are both rather long and tubular, 

 and the cloacal siphon is particularly so (PI. VII, fig. 8). 



From the oesophageal opening being situated near the posterior 

 corner of the pharynx, the viscera extend to the posterior end of 

 the body. The stomach is rounded in form and considerably wider 

 than the intestine. The course of the intestine has been sufficiently 

 indicated above. 



The ganglion is remarkably elongated, being six times as long as 

 broad ; it extends from the level of the fifteenth to that of the 

 twenty-first horizontal bar in the specimen shown in figs. 



The epipharyngeal groove in the same individual is a low furrow, 

 not elevated behind, extending from the dorsal tubercle as far as 

 the ninth horizontal bar, but at the sixth bar its left lip suddenly 

 thins out and bends over the right lip, concealing it from view, and 

 continuing posteriorly as the dorsal lamina. This structure has a 

 very characteristic form in this species (PL VII, fig. 10). It is 

 moderately deep, provided with a regular succession of transverse 

 ribs on its convex side and of well-marked teeth on its edge, the 

 latter corresponding to the number of ribs. There are no inter- 



