2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 75 



characters. Spicules (fig. 3) bifurcated for most of their length. 

 Female with vulva near anus; ovejector and sphincter well developed. 

 The eggs are oval and embr3^onated within the uterus in the one 

 species in the genus represented in our material. 

 Type species. — Sincosta aberrans, new species. 



SINCOSTA ABERRANS, new species 



SpecifiG diagnosis. — Sincosta: Cuticle (fig. 1) of cephalic region 

 coarsely striated transversely. The head measures about 34/x in 

 diameter. Four submedian papillae and 2 lateral amphids present. 

 The esophagus is about 480yu, long by 42/* in diameter near its posterior 

 extremity. Nerve ring not observed. 



Male loosely coiled several times. 4 to 7.8 mm. long with a maxi- 

 mum diameter of 110 to 140/* immediately in front of the bursa. The 

 bursa (fig. 2) is large and composed of two unequal lateral lobes, 

 the right being the larger, with an indistinct dorsal lobe present. 

 The rays of the bursa, in most cases, terminate near the edge of the 

 bursa. The ventro-ventral and the latero-ventral rays on the left 

 side are thick, short, and united in their proximal half, while the 

 equivalent rays on the right side are as thick, but are much longer 

 and are united in their proximal third. The externo-lateral, medio- 

 lateral, and the postero-lateral rays on the right side are united in 

 their proximal third, and those on the left side in their proximal 

 half; on both sides they are divergent and of about equal thickness 

 distally. Each externo-dorsal (fig. 2) arises from an enlarged base, 

 of which the left base usually exhibits, on its median aspect, a slight 

 depression corresponding to and opposite a knob on the right base. 

 The externo-dorsals may be unequal in length; these rays are more 

 slender than the other rays, and may or may not be branched, the 

 absence of the branches being the usual condition. However, as 

 observed in one specimen, branching occurred about 50/* from the 

 distal end of the left externo-dorsal, the size of the branch being 

 approximately the same as the terminal portion of the ray. Dorsal 

 ray absent. Spicules (fig. 3) 475 to 500/* long, and bifurcated pos- 

 teriorly along most of their length, the bifurcation occurring from 

 30 to 76/* from the proximal end. 



It is assumed here that the peculiar situation as regards the dorsal- 

 ray system is due to the suppression of the dorsal ray and the per- 

 sistence of the externo-dorsals. An alternative interpretation is that 

 two dorsal rays are present and the externo-dorsals are suppressed. 

 We accept the first alternative temporarily. 



Female 15 to 19.2 mm. long by 100/* to 200/* in diameter in the imme- 

 diate prevulvar region and tightly coiled in an elongated spiral 

 (fig. 4). The vulva (fig. 5) is a transverse slit located 350 to 450/* 

 from the end of the tail and is supplied with a series of convergent 



