VAX NAME: SIMPLE ASCIDIAXS. 551 
distinguishable externally from T. partitum (Stimpson) by its larger 
size, thicker test, and more coarsely and deeply wrinkled surface, 
even when the pointed process is wanting. 
Mantle very thick and muscular. There are numerous l)ands 
radiating from the siphons and extending to or toward the attached 
end of the body, overlaid by a thick layer of fibers crossing them at 
about right angles and encircling the body. 
Oral tentacles rather few. In a large individual fourteen large- 
sized tentacles (probably representing two orders) were present, and 
some smaller ones in the intervals, making a total of thirty or more. 
Dorsal tubercle of some modification of the U form (often with one 
horn inrolled) with the open interval directed forward or more or less 
to the left. 
Dorsal lamina a plain membrane. 
Branchial sac with four folds on each side, the first usually the high- 
est and the fourth lowest of all. The folds are narrow in comparison 
with the interspaces. Transverse vessels very numerous, of at least 
four orders in the dorsal and five in the ventral part of the sac. Fifth- 
order vessels for the most part merely cross the stigmata. Internal 
longitudinal vessels very numerous, stout on the interspaces and nar- 
row and closely crowded on the upper part of the folds. They are 
separated by from five to eight stigmata on the interspaces between 
folds (by more near the endostyle) . The following was the distribution 
of the vessels on the right side of the sac in a rather large specimen : 
mdi\ 7 (19) 8 (17) 6 (IS) 6 (14) 3 en. 
On the left side there were fewer between the median dorsal vessel 
and the base of the first fold than on the right side. 
Stomach rather long, wide at the cardiac end, and curved nearly 
to a right angle, tapering gradually into the intestine, which forms a 
rather wide short loop. Stomach wall with minute, rather irregular 
longitudinal wrinkles. Rectum long and nearly straight; margin 
of anus with about a dozen rounded lobes. 
Ovaries (one on each side of the body) elongated tubes tapering 
toward each end and bent in deeply sinuous curves; placed in a 
direction more or less nearly coincident with the long axis of the body, 
except that the posterior part of the right ovary is sharply bent in a 
ventral direction, often so as to form less than a right angle wuth the 
rest of the organ. The testes are rounded, oval, or bean-shaped bod- 
ies, each composed of a number of closely crowded lobes of irregular 
