658 



MH. B. F. OUMMINfiS ON LICE 



it is present in all the species except A. cyyni. The plate nnd 

 parameres are fused in one piece, there being no articulation and 

 no trace even of a suture. Parameres : Distally these appendages 

 bend in to meet one anotlier and embrace the median josevido- 

 penis, which is probably endomeral. The parameres are fused 

 with the base of the pseudopeni'i, but not with one another, the 

 tips being quite discrete. Parameres and pseudopenis lie dorsally 

 and curve upwards at the end. Below, in the mesosoma.l space, 

 is the sac — -an interesting structure, slightly expansible (in 

 copulation), and carrying dorsall}^ at its distal end a great 

 number of minute finger-shaped papillfe. Behind these are 

 seen numbers of minute circular spines. On its ventral surface 

 in the hypomeral area is a remarkable retinacular apparatus, 

 consisting of a, semicircidar row (with the apices pointing back- 

 wards) of ten elongate powerful teeth, those in the middle 

 as long as the pseudopenis; it is uncertain whether this comb 

 of teeth can be moved foi'ward or not. Below the sac is the 

 'endomeral plate, which, lik;e the parameres' is continuous with 

 the basal plate. Fixed upon the posterior margin dorsally is 

 tbe densely chitinised eiiractor. It is a little, more or less oval 

 piece of dark-brown shiny chitin, running out into two limbs 

 behind — a dorsal and a ventj-al, the one immediately above the 

 otlier. The ventral limb is blunt at its tip, the dorsal more 

 ■acute, the two together recalling a tin-opener without the 

 handle. 



A. obtusus. — Yery similar to the apparatus of the preceding 

 species, so that it is sufficient to signal the difierences. The basal 

 plate is different in shape in the neighbourhood of the effractor ; 

 the teeth of tlie retinacular comb are shorter and more numerous, 

 being fifteen or sixteen or more in number; and, lasth^, the 

 effractor has a different shape, being distinguished b}^ the narrower 

 and more elongate dorsal limb, which is set in the ventral process 

 of pyriform outline as in a sort of pedestal. 



Group B. Those without the effractor. Correlated with its 

 complete absence, is the complete absence of the retinacular 

 comb. 



A. cygni. — Basal plate : Short and broad, posterior V-shaped 

 mai'k absent. Parayneres : Broad at the base, at the apex blnnt 

 and fused closely with the pseudopenis, which is quite short. 

 Two minute white circles on the posterior margin of the endo- 

 meral plate — probably the relatively large alveoli of minute 

 sensory hairs. 



A. icterodes. — Basal plate : Short and broad ; the V-shaped 

 mark present. Pairwieres : Longer than the basal pla,te, and 

 enclosing a space of different shape from that of A. hruvveiceps, 

 with which it must be compared. 



A. hrumieiceps. — In this species the apparatus, very similar to 



