292 Annals of the South African Museum. 



? . The head is longer and broader than in mirabilis. The 

 internal incrassations of the lateral bands of the abdomen are also 

 more pronounced. 



Dimensions of GIEBELIA HEXAKON. 



Length. Breadth. 



585 -585 



185 -406 



171 -471 

 1-040 



75 



1-97 



076 -050 



056 -030 



030 -030 



026 -026 



040 -023 

 Length of Antennae '23 -22 



GEN. MACKAYIA, Waterston. 



Mackayia, Waterston, Ann. Scott. Nat. Hist. p. 251 (1913). 

 MACKAYIA HETERACANTHUS, Waterst. (1912). 

 (PI. XXV., fig. 8; PI. XXVI., figs. 13, 16, 18.) 



Mackayia heter 'acanthus, Waterston, The Scottish Naturalist, p. 258 



(1912). 



$ , ? . Types Procellaria (Ossifraga) gigantea (Giant Petrel). 

 2 $ 3 . Oceanites oceanicus (Wilson's Storm Petrel). 26 : iii : 04. 



P. Bononii, coll. 



Description of M. HETERACANTHUS. 



In general facies and chaetotaxy very similar to M. dimorpJia, 

 Waterst. (The Scottish Naturalist, pp. 251-7, figs. 1-6, 1913), from 

 which, however, it may be separated by the head and $ genitalia. 



$ . Head. Clypeus straight with rounded angles. Bands curved 

 towards one another, anteriorly each bears three short hairs one 

 above, one at the edge, and a third below and somewhat behind the 

 first two. There rises also from below, but farther back, a longer 

 hair which projects beyond the edge. On the upper surface of the 

 clypeus there is a longish hair between the band and the edge of the 

 signature, at about the level of the peculiar labral folding. Signature 

 reaching back to the mandibles, where it fuses broadly with a 

 transverse internal band connecting the antennals. The pre-sutural 

 portion of the signature bears apparently two hairs, but careful 



