NO. 19S9. ASCIDIAN8 FROM NORTHEASTERN PACIFIC— RITTER. 471 



"No label," 12 specimens. 



AJl these stations so far as known, and probably all, are in Bering 

 Sea. 



In giving the number of individuals I have ignored a great many 

 little ones sitting on the large ones. 



Type.— Cat No. 5686, U.S.N.M. 



STYELA HEMIC^SPITOSA, new species. 

 Plate 34, figs. 21-23. 



Superficial characters. — Posterior half or less of body covered by a 

 dense mat composed of short, filiform, more or less mtertwined 

 processes growing on the test, this carrying embedded among and 

 clinging to the processes a quantity of fuie greenish earth. Anterior 

 half or more wholly devoid of the processes, the test here varying 

 from nearly smooth m the flat form to pronouncedly tuberculate, 

 particularly around the orifices in the pyramidal form; the tubercles 

 generally somewhat soft and blister-like, often low and flat and sepa- 

 rated from one another by considerable intervals. Form varying 

 from flat-eUiptical to high conical or cylindrical. Large specimens 

 of the flat form 20 mm. in greatest transverse diameter and 12 mm. in 

 height; large specimens of pjrramidal form 12 mm. in greatest trans- 

 verse diameter, and 15 mm. in height (figs. 21, 22). Siphons absent 

 or very short, near together; orifices inconspicuously four-lobed. 

 Test thin, rather stiff, opaque white where free from discoloration by 

 the mud m which the animals lived. Mantle thin and delicate, the 

 constituent muscle bundles being very fine and close together; mus- 

 culature of nearly equal development over the whole body. 



Respiratory system. — Branchial tentacles varying in number from 

 25 to 40, several sizes, the largest long and strong, laterally com- 

 pressed, the smaUest hardly more than short flattened stubs. Atrial 

 tentacles present in great numbers, more than 100, very fine filiform, 

 all of nearly equal length. Dorsal tubercle spherical, projecting 

 prominently; hypophysis mouth broad U-shape, ends little or not 

 at aU curved, directed forward. Branchial sac with four folds on each 

 side, all low, with wide intervals between them. (For the scheme 

 of longitudinal vessels of sac see Table 11.) Transverse vessels of 

 two sizes, regularly alternating, the smaUer ones usually crossing the 

 stigmata. Stigmata long and open with parallel borders, from 4 to 

 6 between two longitudinal vessels in the spaces between the bran- 

 chial folds. Branchial network generally regular in its elements, 

 as described. Dorsal lamina neither toothed on the edge nor ribbed 

 on the side. Endostyle not prominent, tortuous at the anterior end. 



