NEW SPECIES OF FLAT WORMS HYMAN 431 



Sections of the postpharyngeal region of both specimens failed to 

 show any trace of sex organs. The specific diagnosis therefore rests 

 on shape and color pattern. 



Locality. — Type and paratype collected at San Jose, Costa Kica, at 

 1,160 meters, by M. Valerio, Jnne 15, 1929. 



Type. — U.S.N.M. 20409, including serial sections of pharynx and 

 adjacent region. Paratype, U.S.N.M. no. 20410, including also a piece 

 removed for sectioning. 



Family RHYNCHODEMIDAE 

 Genus RHYNCHODEMUS, Leidy, 1851 



RHYNCHODEMUS TERRESTRIS (O. F. Mullcr, 1774) 



Figure 50, 6, c 



Material examined. — A single specimen. 



Description. — Specimen 12 mm long, cylindroid, both ends rounded, 

 anterior end larger than posterior (fig. 50, &), this probably the result 

 of contraction. Eyes not seen in the whole specimen but found in 

 sections as a pair at the anterior tip. Cut into sagittal serial sections, 

 but through the mistake of trying to stain the slides before the sec- 

 tions were fully dried the series was badly damaged. Sufficient re- 

 mains, however, to enable one to reconstruct the copulatory apparatus. 



Reproductive system. — The genital system was found to be so 

 nearly identical with that of the European Rhynchodemus terrestris 

 that after some indecision the specimen is placed in that species. The 

 slight differences found are probably the result of various degrees of 

 contraction and do not seem to warrant the erection of even a variety. 

 Sagittal view of the copulatory apparatus is shown in figure 50, c. 

 Genital pore communicates with genital atrium by a long canal; 

 genital atrium occupied by the penis. Penis with well-developed bulb 

 and papilla ; papilla and bulb more elongated and slender than shown 

 in figures of European specimens (e. g., by Bendl, 1908), but this 

 probably is the result of a greater extension. Penis and bulb ex- 

 tremely muscular with a longitudinal muscle layer under the flat- 

 tened epithelium of the papilla ; bulb with numerous strong transverse 

 fibers, appearing like a network. Each vas deferens enlarges slightly 

 near the penis bulb to an external seminal vesicle, then narrows again, 

 and enters the bulb where both join an elongated seminal vesicle lined 

 by a high glandular epithelium. In European specimens this internal 

 seminal vesicle is figured as a large rounded sac ; in the present speci- 

 men it is elongated, but this again is referable to the extended state 

 of the penis. In the penis papilla, the seminal vesicle narrows to an 

 ejaculatory duct lined by a flat epithelium, which proceeds to the 

 penis tip. Floor and rear of genital atrium lined by a very high 



