4 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 75 



atrophied. Spicules very small, similar in form but unequal in size, 

 the left one more than twice as long as the right. Female unknown. 

 Habitat, orbital cavity of birds. 



Type species. — Aproctoides lissum, new species. 



This genus is unquestionably closely related to Aprocta but differs 

 from all the species included in that genus in two characteristics; 

 first, in the division of the esophagus into two distinct portions and, 

 second, in the very marked difference in the length of the spicules. 

 The latter by itself does not appear to the writer to be a character 

 of generic value, although Yorke and Maplestone separate the Aproc- 

 tlnae from the Filariinae on the basis of similarity and approximate 

 equality of the spicules in the former group and dissimilarity and 

 mequality in size in the latter. There would appear to be as much 

 justification for splitting up the Filariinae of Yorke and Maplestone 

 into a number of subfamilies, since they differ so greatly in the form 

 of their spicules, as for separating off one group in which the spicules 

 chance to be approximately equal and not widely different in struc- 

 ture, especially in view of the fact that these two characteristics tend 

 to go together. The character of the esophagus, however, especially 

 when accompanied by another minor difference, seems to the writer 

 sufficient reason for the erection of a new genus. Furthermore, in 

 the male at least, the posterior part of the intestine is not degenerate 

 or atrophied, but according to Railliet and Henry (1910) and also 

 Skrjabin (1917a and 19176) the absence of an anus and the atrophy 

 of the posterior part of the digestive tract appears not to be a char- 

 acteristic of the genus Aprocta as was at first thought to be the case 

 by von Linstow (1883). In some species at least the posterior end 

 of the digestive tract is very much attenuated. 



APROCTOIDES LISSUM, new species 



Figs. 5 and 6 



Specific diagnosis. — Aproctoides : 



Male 12 mm. long with a maximum diameter of about SSO/i; both 

 ends bluntly rounded, the diameter at the posterior end of the 

 esophagus being about 300a/, and just anterior to the cloaca about 

 215/u. Cuticle smooth, without either transverse or longitudinal 

 striations. Mouth provided with three very inconspicuous flattened 

 lips. Anterior portion of the esophagus about 155^ long, with 

 rather ill-defined and not quite cylindrical sides; posterior part about 

 575iu long, cylindrical, with sharply defined walls, somewhat broader 

 than the anterior part, with a uniform diameter of about 105/i. 

 Genital tube much folded and twisted, but not spirally wound 

 around the intestine. Tail bluntly rounded, the cloaca situated on 

 a conspicuous prominence about 145m from the posterior end. 

 Spicules similar in form, much broader proximally than distally, and 



