460 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.58. 



20 mm. long and 0.9 to 1.25 mm, in maximum diameter. Mature 

 males about 8 to 10 mm. long, with a maximum diameter of about 

 0.6 mm. Anterior region of body provided with four circles of 

 cuticular spines which are approximately 24[l in length. Proboscis 

 provided with four circles of five hooks each, those of terminal and 

 second circle similar in appearance and size and fairly sharply dif- 

 ferentiated from those of third and basal circles. Terminal hooks 

 94 to 106tx long, with a root 47 to oSjji. long; those of second circle 

 76 to 100[JL long, with a root 47 to 53p. long ; those of third circle 53 

 to 59iJL long, with a root 24 to 30[x long; basal hooks, 41 to 47ii long, 

 with inconspicuous roots 12 to 24[x in length. Lacunar system an 

 irregular system of branching canals. Subcuticular nuclei of two 

 types; those in anterior extremity ovoid giant nuclei; those in pos- 

 terior part of body, each in the form of a central elongated mass, 

 from which short lateral branches are given off. Anterior nuclei, one 

 dorsal and one ventral. Hemaining nuclei lateral in arrangement, 

 usually one upon the left and two upon the right side of the body. 

 Proboscis receptacle inclosed by a single muscular wall. Central 

 nervous system a single ganglion, near posterior end of receptacle. 

 Testes elliptical to spindle shaped, usually considerably separated 

 from each other. Cement gland a long compact mass containing 

 a few large nuclei. Female genital orifice on ventral surface of the 

 body a short distance from the posterior tip (fig. 19). Posterior 

 extremity of body beyond genital orifice of distinctly smaller diam- 

 eter than remainder of body. 



Type host. — Hoplias malaharicus (Bloch). Also taken from the 

 following hosts: Symhranchus marmoratus Bloch, Crenicichla ge- 

 ayi Pellegrin, Gephyrocharanc valenciae Eigenmann, and Astyanax 

 hima-culatus (Linnaeus). Identified by Prof. C. H. Eigenmann. 



Tyjye locality. — Maracay, Lake Valencia, Venezuela. Also taken 

 at Tsla del Euro, Venezuela. 



Cotypes in the collection of the writer and in the United States 

 National Museum. 



The description of this species is based upon a study of numer- 

 ous individuals from various hosts, all collected during the month 

 of August, 1918. They represent widely different conditions of ma- 

 turity, ranging from fully mature individuals to much smaller 

 specimens, in which the sexual products are not yet differentiated. 

 This diversity of conditions has offered exceptional opportunity for 

 the complete study of the finer features of the morphology from 

 stained toto-mounts, for many structures, partially obscured in the 

 gravid females, have been readily demonstrable even in these same 

 individuals after the general nature of the structures had been de- 

 termined from a study of smaller, less fully developed specimens. 



