POLYCLABS OF THE ATI^NTIC COAST HYMAX 475 



aperture into rear wall of genital atrium but the actual connection, 

 although I do not doubt its existence, could not be seen on the sections. 

 Vagina then proceeds dorsally and appeai-s to make a downward bend 

 as a ductus vaginalis opening ventrally by a large pore behind the 

 common genital pore (fig. 29, c) ; but as indicated in the figure the con- 

 tinuity could not be entirely traced. Vagina and ductus vaginalis 

 with moderately muscular walls of inner circular and outer longitudi- 

 nal fibei^s. From dorsal end of ductus vaginalis duct proceeds pos- 

 teriorly and appears to receive the much-swollen uteri ; hence this duct 

 is seemingly the connection of the uteri with the vagina. Its conti- 

 nuity with the ductus vaginalis was perfectly clear on the sections; 

 but as already noted the continuity of both with the vagina could not 

 be established. The complete elucidation of this very interesting 

 species must await the finding of further material. 



Distribution. — St. Josephs Bay, Fla., five individuals taken by 

 Pearse in March 1936 (whereabouts of the other four specimens 

 could not be ascertained). 



Habits. — Among ascidians on pilings. 



Type. — One whole mount; sexual region as serial sections (2 

 slides), U. S. N. M. No. 20533. 



Remxirks. — This is the third species that Pearse called Leptoplana 

 angusta. It is the specimen mentioned by Pearse (1938, p. 77) as 

 collected at St. Joseplis Bay, Fla., March 28, 1936. The drawing, 

 fig. 4, pi. 20, in Pearse and Littler labeled Leptoplavxi angusta is also 

 D'lgynopora aniericana. This drawing purports to represent a 

 Beaufort polyclad, but actually the individual from which the draw- 

 ing was made is the type specimen of Digynopora amencmia^ from 

 Florida. Tlie species from around Beaufort which Pearse and 

 Littler confused with the Florida form is Eupl/ina carolinensis. de- 

 scribed above. 



The presence of a ductus vaginalis, i. e., a canal leading from the 

 vagina to an accessory external opening or looping back to reenter 

 the vagina near the regular genital pore, is not uncommon in acoty- 

 lean polyclads. Bock (1925) has discussed its occurrence and has 

 pointed out that this condition is particularly apt to develop in the 

 families Leptoplanidae and Stylochidae. Genera 'with a ductus 

 vaginalis lack Lang's vesicle. Three lej^toplanid genera have already 

 been based on the presence of a ductus vaginalis. These are Tri- 

 pylocelis Haswell, 1907, in which the ductus opens externally hy a 

 pore behind the regular female pore and the male apparatus re- 

 sembles Euplana; Gopidopluna Bock, 1913, with a similar ductus 

 vaginalis, and male apparatus as in Notoplana; and Ceratoplana 

 Bock, 1925, in which the ductus makes a loop, reentering the vagina, 

 and the male apparatus resembles that of Stylochoplana. I had 



