28 UNITED STATES NATIONAL MUSEUM BULLETIN 251 



much longer than measurements given above, because some extended 

 thoraces found in the colony reach 4 mm. in length. Branchial aper- 

 ture 6-lobed. Atrial aperture round or 6-lobed, openmg at tip of 

 short siphon projecting at level of first stigmatal row. Atrial languet 

 distinct, far anterior to atrial siphon; location somewhat variable — 

 just behmd dorsal ganglion in some zooids, slightly anterior to gan- 

 glion in others (fig. 36). Nine fine, longitudinal muscles on each side 

 of thorax. Stigmatal rows 4, about 8 stigmata in each row. A wide 

 space between peripharyngeal band and first stigmatal row, also be- 

 tween fourth stigmatal row and posterior end of branchial sac. Ten- 

 tacles about 10 ; ciliated groove an oval opening ; dorsal languets very 

 distinct and slightly displaced to left of dorsomedian line. Anus 

 bilobed and situated at level of third transverse vessel. Stomach sit- 

 uated at middle of abdomen, with 5 longitudinal plications when the 

 narrow typhlosole and four wider ordinary plications are counted 

 together. Proximal end of rectum constricted from foregoing part 

 of alimentary canal; but no caeca are formed there. Ova found 

 near middle of range between the posterior end of intestinal loop and 

 frontal end of testis. Testis not fully matured, follicles arranged in 

 two rows ? 



Remarks. — Fewer stigmatal rows and the situation of the atrial 

 languet widely apart from the atrial siphon are the characteristics 

 of the present species. Amaroucium distomoides Herdman, 1899, from 

 Port Jackson, Australia, closely resembles the present species in that 

 its zooids have 3 or 4 stigmatal rows. However, the test of the 

 Australian species is free from sand grains. Although in many 

 forms this feature cannot be regarded as a significant character- 

 istic to separate species, the localities of the two species are so far 

 apart from each other that the conspecificity of these species is quite 

 impossible. 



4. Aplidium yezoense, new species 



Figure 4 



HoLOTYPE. — USNM 11802, Japan: Hokkaido Island, Hakodate; 

 E. So Morse, collector. 



Pailytypes. — USNM 11803, same data. 



Description. — Seven colonies are in the material, the largest, 

 measuring 30 mm. X 28 mm. in extent, is the holotype. They consist 

 of a number of cormidia and are attached to gravel below. Larger 

 cormidia roughly finger-shaped and may attain 11 mm. in length and 

 5 mm. in diameter. 



Test cartilaginous, pale grayish brown, and slightly translucent so 

 that the reddish brown zooids can be seen faintly through it. Surface 

 smooth and quite free from foreign matter. Common cloacal aper- 

 ture at center of distal end of each cormidium, being surrounded by 



