Some Ectoparasites in the South African Museum. 291 



flap is sufficiently characteristic of this small but remarkable group 

 of parasites. 



GEN. GIEBELIA, Kellogg. 

 Giebeiia, Kellogg, New Malloph. pt. 1, p. 137 (1896). 



GIEBELIA HEXAKON, spec. nov. 

 (PI. XXV., figs. 7 and 11 ; PI. XXVI., fig. 14.) 



$ , 4 $ 2 . Majaqueus aequinoctialis (Cape Hen). 

 One of these ? ? is merely a skin. 



The occurrence of a species of Giebeiia in the Atlantic is interest- 

 ing. Hitherto known as a Puffinus parasite from the Pacific only, this 

 genus proves to have a wider range both in hosts and in distribution. 



A larger paler form than G. mirttbilis, Kell., with which at first 

 we were inclined to identify Dr. Peringuey's material. On com- 

 parison with a pair of paratypes forwarded by Professor Kellogg 

 some interesting differences, undoubtedly of specific value, appear. 

 These are to be found (a) in the head, (6) genitalia $ , and (c) in the 

 shape of the marginal bands of the abdomen. In general chaetotaxy 

 these Giebeliid forms are practically identical (see under Mackayia 

 heter acanthus}. We therefore draw attention merely to the following 

 features. 



$ . The head is proportionately broader behind in liexakon than 

 in mirabilis. The antennae are quite simple. In fact the general 

 facies of the head is reminiscent of 5 mirabilis rather than the $ . 

 The projecting knobs of the membranous fold are large. A unique 

 feature, reminiscent also of the ? ? of this group, is the presence in 

 the J of a short backwardly curved branch of the antennal band 

 which bears terminally just above the base of the antennal joint a 

 heavy spine. The 4 similar spines of mirabilis are also present, and 

 from these 6 pike-like outgrowths the species is named. 



On the inferior aspect of the head the eye is produced into a 

 short blunt hooked process directed forwards. The eye itself, as in 

 mirabilis, is extremely prominent. The greatest width of the head 

 lies between the eyes. In the allies of hexakon the greatest width is 

 just below the eyes. There is almost no difference in shape or 

 dimensions between the heads of the sexes in this species (see 

 tables), but the ? temples swell out slightly beyond the eye. The 

 genitalia $ are quite distinct from those of mirabilis. The basal 

 plate is longer and narrower. The paramera are bent only at their 

 articulation with the plate. Thereafter they run with parallel sides 

 to near the apex. The penis is longer than in mirabilis. 



