128 UNITED STATES NATIONAL MUSEUM BULLETIN 251 



on right side; chamber empty in all examined zooids. Thoracic 

 mantle light purplish brown; anterior part of thorax, areas along 

 endostyle and around its posterior end pigmented more darkly ; ten- 

 tacles, peripharyngeal band, and transverse vessels pigmented rather 

 heavily. 



Stomach situated at level of posterior one-fourth of abdomen. Hind 

 stomach and midintestinal portion well defined. Proximal end of 

 rectum constricted markedly from preceding part of alimentary canal, 

 but no caecum formed. Wall of rectum betw^een level of middle 

 of hind stomach and that of cardiac end of stomach somewhat whitish, 

 due to circumintestinal gland consisting of many fine tubules running 

 very irregularly and complicatedly. Testicular follicles small, not 

 numerous in all examined zooids (which may not yet have fully 

 matured). Ovary located at level between pyloric end of stomach 

 and middle of hind stomach. 



Remarks. — The existence of common cloacal apertures on the colony 

 surface and the opening of atrial apertures on the inner surface of the 

 hypothoracic lacunae allude to the close relationship between the 

 present specimen and Distoma deerrata Sluiter, 1895, and Polycitor 

 coalitus Sluiter, 1909. In the latter two species, however, the abdo- 

 men is rather short, roughly as long as the thorax and with no spacious 

 intermediate area between the peripharyngeal band and the first 

 stigmatal row. Stigmata 12 to 13 in each of three rows in P. coalitus 

 and only 4 in D. deerrata; in the latter rudimentary stigmatal row 

 is at the posterior end of the branchial sac, consisting of 3 to 4 round- 

 ish orifices. Zooids of both Polycitor torosus Sluiter, 1909, and P. 

 ianthinus Sluiter, 1909, closely resemble those of the present specimen 

 in having an atrial siphon issuing from the posterodorsal corner 

 of the thorax. In these two species, however, the atrial aperture opens 

 directly to the exterior on the surface of colony ; the lacunae and the 

 common cloacal apertures are never formed. There are 12-18 (up to 

 20 according to Van Name, 1918) stigmata in each of three rows in 

 P. torosus and 10-12 (up to 20 according to Van Name, 1918) in P. 

 ianthinus. In the latter, a spacious intermediate area is between the 

 peripharyngeal band and the first stigmatal row as in the present 

 specimen, whereas it is absent in P. torosus. The atrial siphon of 

 P. ianthinus is provided with a longitudinal musculature. Thus, it 

 is evident that the present specimen forms, together with D. deerrata 

 and P. coalitus^ a peculiar group characterized by the existence of 

 the lacunae system in the colony and resulting in common cloacal aper- 

 tures, while P. ianthinus and P. torosus represent an intermediate state 

 between the forms of this group and many other forms belonging to 

 the common Eudisfoma-type. 



