28o CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



expanded. The sheath (fig. 9, s. f. and fig. 7) is tubular 

 basally, but terminates in four long lobes embracing the 

 penis (fig. 7). Two of these (/. /.) are lateral and symmet- 

 rical. They are larger than the others and are notched at 

 their ends. The ventral lobe {vent.) is a wide trough-like 

 plate; the dorsal one {dor.) is a thin narrow blade. 



Posterior lateral clasping appendages are lacking. 



The lateral lobes of the tenth segment (pi. xxxii, fig. 2) 

 have in this species the appearance of being clasping 

 organs. Each is large, elongate, somewhat constricted at 

 the middle, and bears on the inner face a large flat brush 

 of long thick flat curved hairs. 



Psilopus pilicornis Aldrich. 



This form is essentially the same as the last. The penis 

 has a large concave sheath below, a tongue-like guard 

 above, and two large wide protective lobes laterally. 



Neurigona superbiens Loew. 

 Plate XXXI, Figs. 5 and 8. 



The pregenital part of the abdomen in this species is 

 oval. The peduncle of the hypopygium, formed of the 

 seventh segment (fig. 8, vii), projects downward, and the 

 hypopygium is turned forward upon it. The eighth seg- 

 ment (viii) is short and oblong, elongate dorso-ventrally, 

 and lies upon the anterior lateral aspect of the ninth. The 

 latter, however, projects forward strongly on the right side. 



The hypopygium is thin-walled, semimembranous, and 

 almost fleshy in consistency. It is formed almost entirely 

 of two large lateral quadrate plates with rounded angles. 

 This structure is due to the great shortening of the dorsum, 

 and consequently also of the roof of the genital chamber. 

 Within the lateral plates are inclosed most of the penis, the 

 posterior clasping appendages, and the lobes of the tenth 

 segment. 



