xo. 14 



INSECT A P.no M K N — S NODGR ASS 



27 



of the operculum {Fai). The origans of the female are essentially 

 like those of the male, and open on a pair of similar papillae. 



The oi)erculum (fig. 9 A, 1)) clearly includes in its composition 

 a ])air of appendages similar to the following gill— bearing appendages 

 ( C. D), but the median membranous area of its base (B, V), on 



ill-bearing appendages of Xipho- 



FiG. 9. — Xiphosurida: operculum and first 

 sura Polyphemus, male. 



A, anterior (under) surface of operculum. B, posterior (upper) surface of 

 operculum, with penes on median membranous area of base. C, first opistho- 

 somal appendages, anterior (under) surface. D, posterior (upper) surface of 

 right first opisthosomal appendage and median membrane. 



a-1, subdivisions and sutures of appendages (see text); Brn, branchiae; ;;;. 

 median tongue of venter; Pen, penis; V, membranous venter of segment between 

 ba.ses of appendages; I'd, vas deferens. 



which are situated the genital papillae, appears to be a fold of the 

 venter of the opercular segment intercalated between the lateral appen- 

 dicular elements. In the following segments the median membrane 

 entirely separates the appendages (C, D, V) and ends with a free 

 distal process (D, m) between them. The genital openmgs of the 

 Xiphosurida, therefore, are situated, not on the bases of the appen- 

 dages, but on the venter of the eighth segment, as in the. Arachnida. 



