576 PROCEEDINGS OF THE NATIONAL MUSEUM vol. i08 



ruffled pharynx of the butterfly type, single male gonopore, and 

 coloration should aft'ord recognition. 



Holotype: The larger specimen, USNM 28657. 



Pseudoceros tristriatuSf new species 



Figure 11a 



Pseudoceros concinnus, Stummer-Traunfels, 1933, p. 3565, fig. 9 on color pi. 

 Not Proceros concinnus CoUingwood, 1876, p. 90, fig. 4, pi, 17. 



Material : A single specimen was taken from beneath rocks on the 

 seaward shore of Ella Islet, Ifaluk Atoll, western Carolines, Sept. 20, 

 1953, by F. M. Bayer under the auspices of the Pacific Science Board 

 Atoll Research Program. 



General characters: The preserved worm (fig. 11a) is of oval 

 form, measuring 12 by 5.5 nam., but a color photograph taken by 

 F. M. Bayer shows that it is more elongated in life, about 4 times as 

 long as broad. The preserved worm is entirely black but in life it is 

 light blue with three longitudinal orange stripes. These stripes appear 

 faintly bordered with black and extend from shortly behind the 

 tentacles almost to the posterior end. The two lateral stripes are 

 confluent posteriorly behind the median stripe. In the preserved 

 worm the tentacular folds are fairly well retained and a few eyes can 

 be seen upon them. Behind their bases is a rounded cluster of cerebral 

 eyes but the eye arrangement could not be satisfactorily ascertained 

 because of the dense black color of the preserved worm. The pharynx 

 is of the butterfly type, that is, with pronounced lateral lobes increasing 

 in length posteriorly where they slant backwards. Behind the 

 pharynx the main intestine is conspicuous in the cleared worm, giving 

 off numerous side branches that enter a dense black network of 

 intestinal branches spread throughout the body. The sucker is 

 located about 5 mm. from the anterior end in the preserved specimen. 

 The worm is juvenile, being devoid of any traces of the reproductive 

 system. 



Holotype: USNM 28659, one whole mount. 



Remarks: Despite the immaturity of the specimen, the very dis- 

 tinctive color pattern justifies giving it a name. I believe this 

 specimen is identical with the one figured in Stummer-Traunfels 

 (1933, fig, 9 on col. pi. following p. 3596), which he identified as 

 Pseudoceros concinnus (CoUingwood). I believe this identification is 

 erroneous, for Collingwood's colored figure gives an entirely different 

 color pattern: cream with a blue border and blue middorsal stripe. 

 I previously called attention to Stummer-Traunfels' error when I 

 described as P. concinnus specimens from New Guinea (Hyman, 1954). 

 Stummer-Traunfels' colored figure that I regard as identical with the 



