72 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



coarsely wrinkled, being stained with mud but without much ad- 

 herent foreign matter. Diameters of one of the largest specimens, 

 antero-posterior 18 mm., dorso- ventral 16 mm., transverse 16 mm. 



When removed from the test the lobation of the branchial aper- 

 ture is still obscure; the atrial aperture is square. Mantle muscula- 

 ture strong on dorsal part of body; sphincters of the tubes strong 

 and thick. Numerous closely placed circular muscle bands surround 

 the bases of the tubes. Fairly numerous and stout radial bands also 

 extend from each tube nearly or quite to the ventral region, and are 

 crossed by narrow and more numerous transverse or circular bands, 

 forming a network very dense on the dorsal part of the body, but 

 more open as the ventral region is approached. 



Figs. 6-11. — Ctenyuba intermedia, new species. 6, Left and right sides of body. 

 X 1.5. 7, Tentacle, x 15. 8, Dorsal tubercle and part of dorsal lamina. X 5. 

 9, Part of branchial sac. X 15. 10, Hepatic tdbdles. X 5. 11, Part of 

 gonad. X 6. 



Tentacles only moderately numerous, of several sizes, somewhat 

 irregularly distributed. The largest ones apparently number about 

 6 and are 2 or 3 times compound with rather few and irregular 

 branches, but they bear broad membranes. Tips of smallest branches 

 blunt and rounded though scarcely if at all enlarged. 



Dorsal tubercle very large and prominent, horseshoe-shaped with 

 strongly in-rolled horns; open interval forward (observed in a num- 

 ber of specimens). 



Dorsal lamina represented by a series of small closely placed lan- 

 guets. 



Branchial sac with seven very prominent folds on each side, sepa- 

 rated by comparatively narrow intervals. Three orders of transverse 

 vessels regularly arranged; additional still smaller vessels cross the 

 stigmata in some places. Along the summit of each fold the sac is 

 raised into a row of small infundibula, separated from each other by 



