VAN NAME: SIMPLE ASCIDIANS. 483 
The specimen had evidently adhered to hydroid stems by an area on 
its lower surface. 
The other specimen is larger (22 mm. by 18 mm.), but less regular 
in form. It also grew on a hydroid. 
Mantle thin, the musculature rather slight but extended over a 
large part of the surface of the body, though over the region of the 
kidney it disappears almost completely. Musculature composed 
mainly of very slender crooked bands forming a very loose extremely 
irregular network. On the area about the apertures it consists as 
usual of radiating and circular l)ands, but these are neither stout nor 
numerous, nor very regular in their arrangement. The majority 
of the circular bands lie superficial to the radiating ones. 
About six large, pinnately branched, two or three times com- 
pound tentacles, and several orders of smaller and simpler ones 
arranged according to the usual scheme, but with frequent ir- 
regularities. 
Dorsal tubercle simply C-shaped, with the horns neither inrolled 
nor strongly incurved. Open interval turned toward the right. 
Owing to mutilation of the specimen not much of the dorsal lamina 
or the dorsal part of the branchial sac could be seen; the branchial 
folds could not be satisfactorily counted, but it seems not improbable 
that there were but six. The internal longitudinal vessels are stout. 
They number on the last three folds on the right side (the fourth, 
fifth, and sixth, if the above total is correct) five, four, and three 
respectively. Apparently there was a total of not more than about 
six or seven on any of the folds. The principal transverse vessels, 
extending from the median dorsal vessel to the endostyle appear to 
be of the usual number (five). Along the summits of the folds in each 
of the spaces marked off by these vessels one large infundibulum is 
present (on the last fold sometimes two). These usually divide into 
an anterior and a posterior apex. Between these apices a small trans- 
verse vessel is usually present. 
Stigmata very long and narrow and arranged spirally on the in- 
fundibula. These spirals are, however, not continuous, the stigmata 
ending at intervals, often without being directly continued by another, 
but the general spiral arrangement is maintained by the adjacent 
stigmata, which close nearer together when the one between them 
terminates. In the great length and narrowness of the stigmata 
the branchial sac of this species resembles that of C. lutulenta, but the 
