TUNTCATA. 309 



medium, and sixteen small, but the latter are not all present and the large and medium 

 ones may vary from six to nine each. 



The Dorsal Tubercle is large, prominent and hemispherical. It is marked with two 

 spiral coils (fig. 38). 



Localities :- (1) Five specimens were trawled at Station XIX. in northern part of 

 Palk Bay, depth 4| to 8 fathoms ; (2) one at Station I, oft' Negombo, 12 to 20 fathoms ; 

 and (3) one is labelled " Gulf of Manaar." 



The largest specimen measures 9 centims. x 6 centims. x 3 centims., the two next 

 each 5 centims. x 5 centims. x 2 centims., the next 3 centims. x 3 centims. x 1 centim., 

 and the smallest 2 centims. x T5 centims. x 1 centim. These specimens agree fairly 

 well in most characteristics with Rhabdocynthia pallida (Heller) to which 

 v. Dkasche's Cynthia mauritiana is closely related. These species are described as 

 having onlv eight branchial folds, while the present one has nine. They also differ in 

 the dorsal tubercle, the tentacles and other details, but these are all points subject to 

 individual variation. The large branchial and atrial siphons have strong sphincter 

 muscles, from under the lower edge of which very strong radial muscle bundles emerge. 

 There are about 16 of these on each side at the atrial sphincter, and about 30 on each 

 side at the branchial. The arrangement of these muscles is seen in fig. 37. Large 

 lobed gonads are present on both sides, and show through the mantle as a number of 

 rounded masses (fig. 39), rather different in appearance from the figures of Rh. pallida 

 given by Sluitek and Michaelsen ; however, I believe the difference is only due to 

 stages of growth. The ova occupy the wide central part of the mass, and the spermatic 

 caeca are grouped in clumps around the margin. 



I thought at first, because of the red colour when alive, that this species might be 

 Sltjiter's Cynthia rosea which is a Rhabdocynthia but a closer examination showed 

 that it differed from that form in the details of the branchial sac, in the form of the 

 dorsal languets, and the dorsal tubercle, as well as in the shape of the body and 

 relative positions of the apertures. However, the two species are closely related, and 

 it is a question whether fuller knowledge of both in the future will enable us to 

 unite them. 



This large Ascidian is said by the natives to be characteristic of the West Cheval 

 Paar, but is also found at other places in the Gulf of Manaar. 



Rhabdocynthia ceylonica, n. sp. Plate III., figs. 1 to 19. 



External Appearance. Body of globular or ellipsoidal form, covered with clear 

 pale yellow sand and small shell fragments, except around the apertures. Siphons 

 prominent, the atrial rather the longer ; both on anterior end, and connected by a 

 ridge of test, which, like the siphons themselves, is bare of sand (fig. 3). The lobes 

 of the apertures are marked with white radial lines (see figs. 18, 19); size about 

 2 centims. x 1*5 centims. 



Test thin, transparent ; containing branched vessels with knobs and also spicules. 



