56 UNITED STATES NATIONAL RHISEUM BULLETIN 251 



Remarks. — Although the system of arrangement of the zooids is 

 quite obscure in all of the present specimens, the existence of a long 

 atrial languet in most of the zooids examined seems to suggest that 

 it may be of the complicated kind found in colonies of Polyclinwni 

 vasculosum. Zooids of the present species are characterized by a 

 larger number of stigmatal rows as compared with P. vasculosum ( 15 

 instead of 12-13) . Although the number of stigmatal rows in the two 

 species may be continuous through some forms containing zooids with 

 an intermediate number of rows, these intermediate forms are very 

 scarce as compared with the two typical forms having characteristic 

 number of stigmatal rows. For this reason, I prefer, at present, to 

 separate these species as Van Name did. 



16. Ritterella sp. aflf. aequalisiphonis (Rilter & Forsyth) 



Figure 17 



fAmaroucinm aequalisiphonis Ritter and Forsyth, 1017, p. 487, pi. 38, fig. 4; 



pi. 45, fig. 61. 

 fSigillinaria aequalisiphonis Van Name, 1945, p. 74, fig. 31 ; pi. 28, fig. 1. 



MATERIAL EXAMINED 



Japan : Hokkaido Island, Hakodate ; E. S. Morse, collector. Many colonies 

 (USNM 11787). 



Description. — Many pieces of colonies encrusted on gravel; the 

 largest is 90 mm. X 55 mm. in extent. Each consists of several club- 

 shaped cormidia ending in roundish tips, the larger cormidia 11-12 

 mm. in diameter, 15-20 mm. in length, dark reddish brown or dark 

 brownish. 



Test rather hard and cartilaginous, impregnated with sand grains, 

 especially dense in the basal portion but sparse m the distal portion of 

 the cormidia ; surface sparsely encrusted with sand grains. The sys- 

 tem of zooid arrangement is quite obscure because the specimens are 

 preserved rather poorly. Many amphipods were found boring in the 

 test of some colonies. Zooids mostly seem to be in resting stage; all 

 thoraces missing, abdomens and postabdomens found embedded in a 

 kind of the mesenchyme tissue. Remaining bodies usually 4.5 mm. in 

 length; postabdomen seems to be long. Only a few small zooids in 

 some small and soft cormidia were found in nearly perfect condition, 

 retaining the thorax ; they are less than 3.5 mm. in length, the abdomen 

 about 11/2 times the length of thorax, which is contracted and has ap- 

 proximately 14 stigmatal rows. Stomach elongated, with 8 longitudi- 

 nal plications on the surface besides typhlosolis, situated near middle 

 of abdomen. A pair of distinct caeca found at proximal end of rectum. 



Remarks. — The existence of 14 stigmatal rows and 8 longitudinal 

 plications on the stomach shows the close resemblance to Amaroudum 

 solidwn Ritter & Forsyth (13-15 stigmatal rows and about 8 longitu- 

 dinal plications on the stomach) from California coast and A, dubium 



