546 PROCEEDINGS OF THE NATIONAL MUSEUM vol. io8 



glandular interior is relatively large; it stands almost erect, although 

 this may be partly caused by contraction, and terminates below 

 in a small, conical penis papilla, which is entered by the ejaculatory 

 duct formed from in front by the union of the two sperm ducts. 

 The latter have definite coats of cu'cular muscles but are not much 

 thickened. Their union produces a small seminal vesicle, also with 

 a coat of circular fibers, and this continues into an ejaculatory duct 

 that enters the base of the penis papilla. 



The female gonopore, distinct from but not far behind the male 

 pore, leads into a vertical female antrum, from which the widened 

 vagina proceeds dorsally, then makes a sharp bend posteriorly, 

 descending to enter the small Lang's vesicle. The common oviduct 

 was seen below the duct leading to Lang's vesicle but its exact point 

 of entrance into this duct was not determinable in the sections. 



Specimen: USNM 28640, anterior part as whole mount, postoral 

 part as sagittal sections (one slide). 



Remarks: The original description of Latocestus pacificus is so 

 meager that certain identification with this species is probably im- 

 possible. The present identification must be regarded as merely 

 plausible. It is based on the small size at sexual maturity and the 

 eye arrangement. Laidlaw (1903a) gave the size of the type specimen 

 with some doubt as 12 mm. and stated that gonopores were present 

 although the gonads were immature. Although the gonads could not 

 be seen in the present whole specimen because of its opacity, the 

 copulatory apparatuses indicate full sexual maturity at a length of 

 11 mm., but the specimen is somewhat contracted and was longer in 

 life. The eye arrangement, especially the long and somewhat paired 

 median streak and the short backward extent of the marginal bands, 

 is very like that shown in the one and only figure of L. pacificus. The 

 anterior end of the latter, however, appears abnormally shortened 

 and part may be missing. Laidlaw unfortunately did not depict the 

 location of the brain with reference to the median streak of eyes and 

 it is impossible to beUeve his statement that the brain was located at 

 4 mm. from the anterior end of a worm 12 mm. long. 



Family Plehniidae Bock, 1913 



Plehnia tropica, new &pecies 



Figure Id-/ 



Material: Several specimens, of which five were usable, taken 

 from the alcyonacean Nephthea by the Stanford team at the Palau 

 Islands, Sta. 254, reef south of Ngaremediu, east end of Urukthapel, 

 Oct. 27, 1955. 



