222 UNITED STATES NATIONAL MUSEUM BULLETIN 251 



defining the posterior area surrounding the atrial aperture; on the 

 other hand the complete lack of descriptions of the gonad in these 

 species makes it difficult to compare these two forms with this new 

 species. G. loyville-thom^oni Herdman, collected at a Challenger 

 station in the South Pacific has six branchial plications on each side 

 and evidently differs from this new species in external appearance, 

 although comparison of the gonad cannot be made between G. wyville- 

 thomsoni and the present new species because of the complete absence 

 of description of this organ in the former. Ritter's G. pyramidalis 

 from the foot of the continental slope west of San Diego, California, 

 cannot be compared exactly with the present new species, as the 

 internal structure of the specimens was evidently damaged; his G. 

 sluiteri from just south of the Aleutian Islands differs distinctly from 

 others by its unique structure of gonads. Some of the specimens 

 collected by the Galathea at the stations in Kermadec Trench and 

 provisionally treated by Millar (1959) under G. suhmi Herdman very 

 closely resemble the present new species in internal structure, includ- 

 ing the branchial sac and gonad, and in the manner of the stalk 

 insertion into the body. However, the arrangement of the prominent 

 papillae on the body surface and the surface structure of the stalk 

 seem to differ clearly between these specimens and the present new 

 species. 



Family Molgulidae 



115. Molgula (Molgula) xenophora Oha 



Figure 101 

 Molgula xenophora Oka, 1914, p. 457, figs. 15-16. 



MATERIAL EXAMINED 

 Japan: Hokkaido Islands; Hakodate. E. S. Morse, coll., 35 specimens (USNM 

 11697). 



Description. — The 35 specimens presented in exchange from 

 Tokyo Imperial University were examined. Unfortunately most of 

 them were damaged, but 7 were found in comparatively perfect 

 condition. Body ellipsoidal, attains 42 mm. in length; surface 

 densely or sparsely encrusted with fine black sand grains, which also 

 impregnate the test; thus test thickens, attaining 2-3 mm. in thick- 

 ness in larger specimens. Some specimens attached to each other, 

 hairy attachment processes from ventral side being entangled. 

 Apertures practically invisible from surface, although narrow siphonal 

 area is discernible on dorsal side, being slightly depressed. On inner 

 surface of test, apertures situated about 7 mm. apart in 34-40 mm. 

 long individuals. Mantle soft, thm, brownish. Transverse body 

 muscles represented by many short pieces of muscle scattered over 

 mantle surface (fig. 101&, c) ; generally 3 pairs of longitudinal rows of 

 these muscle pieces in anterior half of body, 7 rows (3 on right, 4 on 



