278 CALIFORMIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



posterior lobe of the curtain-like fold {cur.) of D. crenatus. 

 The lobes of the tenth segment are comparatively much 

 larger. Their marginal hairs are large, strong, and curved, 

 but are not bent or hook-like. 



Pelastoneurus vagrans Loew. 



Plate XXXI, Figs. 2, 4, and 6, 



The pregenital part of the abdomen in this species is 

 rather elongate and conical, ending with the rather pointed 

 sixth segment. The seventh segment is elongate and cy- 

 lindrical (fig. 2, vii). The posterior ventral lobes (fig. 6, d) 

 of the hypopygium are rather short and simple. Each 

 bears on the dorsal edge a bunch of stiff thick cylindrical 

 hairs and terminally has long tapering spines. The 

 clasping appendages (fig. 6, a and 3) are also rather short. 

 The upper one («) ends in a deflexed head; the lower one is 

 simple, tapering, and slightly curved. The sheath of the 

 penis (fig. 2, s. -p.) is split at the end into two lateral lobes. 

 The part of the penis lying in the sheath is double, con- 

 sisting of two long closely appressed flat blades, each 

 tapering to a point. Arising from the posterior end of the 

 roof of the genital chamber, between the bases of the 

 lateral clasping lobes, is a pair of small flat semi-transparent 

 chitinous appendages (fig. 4). Each bears on its wide 

 oblique posterior margin a dense brush of thick slightly 

 curved hairs. Appendages corresponding to these were 

 not observed in any other species examined. 



Pelastoneurus laetus Loew. 

 Plate XXXII, Figs, i, 3-6. 



This is a somewhat aberrant species in the shape of the 

 lobes of the tenth segment, and in the appendicular parts 

 of the hypopygium. The sheath of the penis has a spe- 

 cially curious development. In P. vagrans the end of the 

 penis sheath is divided into two small terminal flaps, but 

 here the sheath ends in two large fantastic lobes (fig. i, 

 s. f. and fig. 3). The right lobe (fig. 3) is wide basally, 



