D. Keilin and G. H. F. Nuttall 
297 
the presence of a small supplementary gonopod on the right side which dis¬ 
places the otherwise normal gonopods to the left. The specimen contains a 
large number of eggs and shows a vaginal prolapse. 
SPECIMENS 48-65, that is 18 examples, are of § type and show $ characters 
to a varying degree as follows: («) No. 48 has gonopods of normal form 
and size, (b) No. 49 (Text-fig. 14 c) has one sub-normal gonopod, the other 
being invaginated; the gonopods are surrounded by a chitinous band 
originating from the $ ventral plate, this almost annular structure serving 
to explain the abnormality of the $ genitalia in Specimen 7 (p. 287). (c) Nos. 
Text-fig. 13. Pediculus humanus, cross between capitis and corporis, Specimen 47. Posterior 
portion of abdomen, ventral aspect, showing supplementary gonopod (sup. gon.) and vaginal 
prolapse (vag. p.). (K. & N. del.) 
50-65 have the $ genitalia represented by unilateral, bilateral, or median 
invaginated structures of irregular form bearing sensory hairs (Text-fig. 14 B, 
being Specimen 50). In some specimens, for example Nos. 51-52 (Text- 
fig. 15 a and b), one part of the $ genitalia, representing the external organs, 
is invaginated in the form of a darkly pigmented and heavily chitinized 
mass, the other part, representing the vagina, is extruded in the form of a 
vesicle. The $ genitalia in all of these 18 examples are more or less deformed; 
two specimens show the vesica penis protruded, in one it is reduced, whilst 
