456 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.58. 



parasites that great diversification in isolated regions is not sur- 

 prising. 



Through the courtesy of Prof. A. S. Pearse I have been permitted 

 to study an interesting collection of Acanthocephala which he secured 

 in the course of investigations upon the fishes of Lake Valencia, 

 Venezuela, during the summer of 1918. Though data from a fairly 

 large number of fishes was included in this collection, but two 

 species of these parasites were encountered. For one of these, two 

 species of fresh-water fishes acted as definitive hosts, and for the 

 other five species of definitive hosts were recorded. Since each of 

 the parasites here encountered represents a hitherto undescribed 

 genus, it seems advisable to present descriptions of them. This is 

 especially desirable because facts brought out in the study of these 

 new forms seem to present entirely new lines of evidence concerning 

 the relationships of certain genera previously described, and also 

 because it has been found necessary to create a new family for which 

 one of these genera becomes tj'pe. 



This paper forms No. 157 of the series of contributions from the 

 Zoological Laboratory of the University of Illinois. 



PANDOSENTIS, new genus. 



Generic diagnosis. — With the characters of the family Neoechino- 

 rhynchidae, except for the variation in arrangement of giant nuclei 

 within the subcuticula. These do not always lie in the sagittal plane, 

 as in representatives of all the other genera previously included in 

 this family, but are frequently lateral in distributon. Parasitic as 

 adults in the alimentary canal of fishes. Body proper small, devoid 

 of spines. Proboscis short, cylindrical, provided with more than 

 three circles of hooks. Boundary between root and thorn usually 

 not sharply marked. Male genital organs in same arrangement as 

 found in members of the genus Gracilisentis. Testes elliptical, con- 

 tiguous. Cement gland a rounded syncytial mass immediately fol- 

 lowing the posterior testis, with its posterior boundary indented for 

 the reception of the reservoir of the cement gland. Cement gland in 

 only known species contains 16 giant nuclei. Central nervous system 

 at base of proboscis receptacle. Retractors of receptacle emerge 

 from the receptacle at its posterior extremity on dorsal and ventral 

 surfaces. Lemnisci not as long as the proboscis receptacle. 



Type species. — Pandosentis iracundus, new species. 



PANDOSENTIS IRACUNDUS. new species. 



Plate 27. 



Specific description. — With the characters of the genus Pando- 

 sentis. Females about 1 to 1.5 mm. long and 0.4 mm. in maximum 

 diameter; males about 0.6 to 1 mm. long and 0.15 to 0.25 mm. in 



