NO. 2346. TWO NEW ACANTHOCEPHALOUS WORMS— VAN CLEAVE 457 



diameter. Body proper tapering slightly toward each extremity (fig. 

 6), frequently with the ventral surface slightly concave. Proboscis 

 short, cylindrical; in most preserved specimens completely inverted 

 and retracted within body proper by the violent action of the ex- 

 ceptionally highly developed invertor of the proboscis and the re- 

 tractors of the receptacle. In fully extended individual the proboscis 

 (fig. 1) measured 0.09 mm. in length and was of the same diameter. 

 Proboscis bears 22 longitudinal rows of four hooks each. Each hook 

 is embedded in a papilla beyond which only a small portion of the 

 hook protrudes. Hooks of distinctive form, somewhat resembling 

 those of Gracilisentis, with no distinct line of separation between 

 thorn and root and with no sharp contrast in form of hooks in dif- 

 ferent regions of the proboscis. Total length of line connecting base 

 of root with tip of hook when hook is in full side view, 14[j,. The 

 exposed, distal, 8[jl of each hook near the base of the proboscis is 

 bent at almost right angles to the basal portion of the hook (fig. 2), 

 while those at the tip of the proboscis (fig. 4) are slightly less 

 strongly bent. Wall of proboscis receptacle very delicate, composed 

 of a single layer. Invertor of the proboscis excessively developed, 

 filling most of the space within the receptacle (fig. 5). Central 

 nervous system a small mass of ganglion cells crowded into the pos- 

 terior extremity of the receptacle between the posterio-lateral angles 

 of the receptacle where the retractors of the receptacle emerge from 

 the wall. Lemnisci shorter than the receptacle and usually obscured 

 by that structure. Embryos (fig. 9) within the body cavity of the 

 mature female 22 to 28iji. long by ll\t. in diameter. Testes ovoid to 

 spheroidal, contiguous ; followed immediately by a syncytial cement 

 gland containing 16 giant nuclei. 



Type host. — Aquidens pulcher (Gill) ; also taken from intestine 

 of C'renicichla geayi Pellegrin. These hosts were identified by Prof. 

 C. H. Eigenmann. 



Type locality. — Maracay, Lake Valencia, Venezuela. 



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

 States National Museum. 



The members of this genus are of especial interest because of the 

 fact that they show remarkable combinations of characters, which 

 indicate probable relationships to the two distinctly North American 

 genera, Gracilisentis and Tanaorhamphus. In many respects the 

 characters of Pandosentis stand intermediate between those of the 

 two genera just mentioned. General body form and general topog- 

 raphy of the internal organs of both male and female closely simu- 

 late the conditions found in Gracilisentis, though the number of 

 giant nuclei in the cement glad is 16, the same as that found in 

 Tanaorhamphus, as against the 12 found in Gracilisentis. The form 

 of the proboscis and the number and shape of the hooks combine 



