POLYCLADS OF THE ATLANTIC COAST HYMAN 469 



mosed to a network with rounded meshes, in which the ova are often 

 conspicuous. 



Reproductive system. — Fully described and illustrated by Bock, 

 1913, and Hyman, 1939a. Diagnostic features are the spherical pros- 

 tate, elongated penis pocket containing the arched penis stylet, and 

 the long, slender Lang's vesicle. 



D'lstributiov. — Massachusetts northward to Scandinavia, common. 



Habits. — Sluggish, littoral, under stones and on seaweeds, in tide 

 pools, on pilings, also sublittoral to 300 feet. 



Remarks. — This is the commonest polyclad of the north Atlantic 

 coast of North America. Although it seems to me easily recognized, 

 it has been regularly misidentified. Mature individuals are easily 

 identified by the curved penis stylet, seen by putting a little pressure 

 on the animal. Verrill called this species by three different names, 

 Leptoplana variabilis, L. virilis, and L. ellipsoides. Whether it 

 actually is Girard's Polycelis variabilis is difficult to decide, because 

 of the nature of the original description. Since Verrill's time, the 

 species has been commonly called Leptoplana variabilis by American 

 zoologists. Previously I had some little doubt that Verrill's figures 

 of Leptoplana. vanahilh could be certainly identified as N. atomata, 

 since they differ in some details; but these are probably inaccuracies, 

 and the finding of two specimens labeled L. variabilis by Verrill 

 himself confirms the identity. I am also decidedly of the opinion 

 that Verrill's species L. virilis is likewise N. atovutta. I have already 

 expressed m.y opinion that what Verrill mistakenly called L. ellip- 

 soides are specimens of N. atomata. 



Pearse and associates frequently failed to recognize N. atomata. 

 In the collections of the U. S. National Museum there exists a whole 

 mount No. 134562 collected in Baffin Bay by Capt. Robert A. Bart- 

 lett, August 3, 1935, which had been identified by Pearse as Lepto- 

 plana foUvATi. This specimen is figured in Pearse, 1938, fig. 26, where 

 it is called Leptoplana angusta. In Pearse and Walker, the same 

 whole mount is said to be Leptoplana virilis. I have examined this 

 whole mount and find it to be Notoplana atomata. The following 

 three whole mounts in the possession of the U. S. National Museum, 

 which were identified by Pearse as Leptoplana angusta., are also N. 

 atamata^V. S. F. C. No. 15620, Nantucket, Mass., September 8, 1875, 

 81 feet; U. S. F. C. No. 15622 (two slides). Bay of Fundy, off Cherry 

 Island, 1872, 120-150 feet, originally labeled Leptoplana ellip- 

 soides. Notoplana atomata is thus one of the three leptoplanid spe- 

 cies confused by Pearse and his associates under the name of Lepto- 

 plana angusta. 



In addition there were in the material sent by the U. S. National 

 Museum a number of unidentified vials all of which are Notoplana 



