444 PROCEEDINQS OF THE NATIONAL iMUSEVM. vol. 45. 



that seems to me of conse:iuence in the way of the identification. 

 The tentacles of rara are "ahnost unramified," according to Kiaer, 

 the branches being only "small buds." This description does not 

 quite apply to my specimens, since the branches, though small and 

 simple, are more than buds. Again, Kiaer speaks of the dorsal 

 lamina as being "very powerful and high." This structure in the 

 specimens now under consideration is undoubtedly wide for an 

 ascidian of this size, but not excessively so. At first I was inclmed 

 to identify the specimens with E. symmetrica (Drasche, 1884, p. 161), 

 a species very close of kin to rara. But the form of the infundibula 

 and of the intestinal bend seems decisive, the infundibula of symmetrica 

 being flat, while in rara they are distinctly elevated. In the "wide 

 rapidly rising look" of the intestine, too, the Alaskan specimens agree 

 closely with rara. It should be mentioned, however, that in the 

 number of stigmata to each infundibulum our specimens seem to 

 correspond more nearly with symmetrica, the number being at least 8 

 in ours, whereas 6 or 7 is the number for the typical rara. But this 

 disagreement does not seem to me to ^o far toward offsetting the 

 agreements above mentioned. 



Specimens collected by W. II. Dall at Kyska Harbor, Alaska, 9 

 to 12 fathoms (No. 1000). 



RHIZOMOLGULA RITTERI Hartmeyer. 



Rhizomolgularitteri B.ARTMEYER, 1903, p. 168, pi. G, fig. 1; pi. 9, figs. 5-9. — Hart- 

 meyer, 1909a, p. 1321. 



Comparison of the numerous specimens of this species in the col- 

 lection with R. arenaria Ritter, reveals the following well-marked 

 differences: The sand coating of arenaria is distinctly thicker thaji 

 in any of the specimens of ritteri, where at its minimum the sandiness 

 is sparse, leaving considerable areas of the test entirely exposed. 

 The mantle musculature, particularly the bands radiating from the 

 orifices, is much stronger in arenaria. The branchial folds are higher 

 in arenaria, the number of longitudinal vessels on them being some- 

 what greater. Hartmeyer has pointed out all these differences, except 

 that of the difference in extent of the sand covering. He also notices 

 the apparent absence of stigmata between the folds of arenaria as 

 being distinctive. I have to correct my description of arenaria by 

 stating that stigmata do occur between the folds. They are, how- 

 ever, fewer as compared with those in the folds than in ritteri, and 

 are disposed more definitely in spirals and low infundibula. In no 

 instance have I seen them in the serpentine partly coiled form charac- 

 teristic of these stigmata in ritteri. 



Albatross stations: 3229, 8 fathoms, 58° 40' N.; 157° 15' W. 

 (Bering wSea), May 31, 1890, 80 specimens.— 3266, 24 fathoms, 55° 08' 

 30" N.; 163° 30' 30" W. (Bering Sea), June 25, 1890, 50 specimens.— 



