CATALOGUE OP TUNICATA. 47 



phallusioides, a specimen of Microcosmus Drasclrii and several small 

 Ascidians, of globular form and encrusted with sand, which prove to be 

 specimens of Molyula Forbesi. 



The very slightly developed mantle shows no muscle bands, but 

 merely microscopic fibres running in various directions. This very 

 slight development of the musculature and resultant absence of power of 

 contraction, is obviously correlated with the stiff inflexible test to which 

 the mantle is attached. In the gelatinous connective tissue of the 

 mantle (PI. Cyn. XVII., fig. 9) we find imbedded the reproductive 

 elements, little ovate clumps or patches of Ova in various stages of develop- 

 ment, and triangular spermatic vesicles with long straight ducts, which 

 unite in small groups just before opening into the peribranchial cavity. 



The branchial sac (fig. 6) is well formed, and the stigmata are large 

 and regular. The simple dorsal tubercle and the tentacles are shown in 

 figs. 7 and 8, on PI. Cyn. XVII. 



Polycarpa rigida, Herdman, PI. Cyn. XVIII., figs. 1 4. 



This is a species which was obtained in Bass' Strait by the "Chal- 

 lenger" Expedition. In the present collection there are about a dozen 

 specimens, 5 from Port Jackson, and the rest from Port Stephen at a 

 depth of 20 to 30 fathoms. One of the specimens from Port Jackson is 

 figured (fig. 1.), because of its somewhat curved shape; the others are 

 more like that figured in the "Challenger" Eeport. Some, however, 

 have the atrial siphon considerably elongated. The smaller Ascidians 

 adhering to our specimen are Polycarpa viridis, Herdm. 



The dorsal tubercle is somewhat variable ; 2 specimens examined 

 had the forms shown in figs. 2 and 3. In another case the tubercle w T as 

 reversed, the opening being directed posteriorly. The dorsal lamina is 

 shown in fig. 4. The branchial sac may have every 6th or every 12th 

 transverse vessel wider, the meshes may contain from 6 to 12 stigmata 

 each, and the internal longitudinal bars may be from 10 to 12 on a fold, 

 and from 6 to 8 in the interspace/" The tentacles may be 20 larger and 

 20 smaller, placed alternately. A very characteristic point about this 

 species is that the test is so thin, and so completely permeated by sand 

 grains, that it becomes stiff and rigid, but very brittle. 



Polycarpa viridis, Herdman, PL Cyn. XVIII., figs. 1 and 5 10. 



This species was originally found by the " Challenger " Expedition at 

 Port Jackson, where the specimens in the present collection are also 



* Compare " Challenger " Report, p. 17(5. 



