PACIFIC TUNICATA OF U.S. NATIONAL MUSEUM 155 



earlier stages, but becomes so voluminous and comj^lex in configura- 

 tion with growth that at last it spreads over four stigmatal rows 

 (fig. 60a). 



IvEMARKs. — Zooids of the present colonies are smaller and with 

 slightly fewer stigmatal row^s than those of the colonies described 

 under the name of Botryllus rufus (Oka) from Japanese waters, 

 which are about 4 nun. in length and have 14-15 stigmatal rows. 

 However, the general appearance of the colony and that of the zooid, 

 especially the existence of the remarkably long rectum, are common 

 to both the present specimen and B. rufus. Therefore I wish to treat 

 B. 7'ufus from Japanese waters as a synonym of B. niagnicoeciis 

 (Hartmeyer). 



76. Botryllus compositus, new species 



Figure 61 



HoLOTTPE.— USNM 11709 : Kangoon, Burma. G. E. Gates. 



Description. — A single colony from Burmese waters was examined. 

 It is roughly oval in outline, 40 mm. X 24 mm. in extent and 14^15 

 mm. in thickness, consisting of a number of cormidia which are less 

 than 13 mm. X 7 mm. in extent and most frequently assume the form 

 of a 23olygonal prism having about 6 mm. diameter (fig. Glc), al- 

 though they may be irregularly lobate (fig. 616). 



Surface encrusted with fine sand grains. Zooids arranged regu- 

 larly in circular systems, each consisting of 7 to 10 zooids. Zooidal 

 layer 2-2.5 mm. in thickness, encrusted with sand only sparsely on 

 surface; test of this part soft, gelatinous, transparent, not impreg- 

 nated with sand grains. Pinkish zooids seen through test of upper 

 surface, with sand grains missing above zooids. Larger lower 

 part of cormidium below zooidal layer covered densely with sand 

 grains; test there soft, gelatinous, translucent or transparent, and 

 contains fascicular vessels sparsely within, but no sand grains. 

 Zooids about 2 mm. in length, embedded perpendicularly in test. 

 Atrial aperture situated at level of first stigmatal row, with a distinct 

 tongue-shaped languet. Stigmatal rows 8-11 on right and 9-12 on 

 left side. Stigmata arranged (D = dorsal, V=ventral) : D 4-5 (1) 

 3(1) 2-3 (1) 2-4 V. Dorsal edge of each row reaches median line. 

 Tentacles 8, larger and smaller ones alternate regularly ; some zooids 

 have minute tentacles in intervals between large and small tent-acles, 

 then number of tentacles increases to 16. Ciliated groove a small oval 

 openmg. Intestine covere posterior one or two stigmatal rows. 

 Stomach located behind branchial sac, situated slightly obliquely and 

 with 9-12 longitudinal plications on surface, excluding typhlosolis. 

 Anus attached to branchial sac at level of seventh to fifth transverse 

 vessel and opens at level of sixth to fourth transverse vessel ; margin 

 plain. A young individual 0.68 mm. long, not yet having communica- 

 tion with exterior, with 11 stigmatal rows on each side, has a rudi- 



206-191—67 11 



