POLYCMTA—BENHAM. 
41 
delicate hairs, extending beyond the tip, surrounding it and more or less concealing it. 
Similar but less developed frills follow and occur along the greater part of the chsetaB 
(fig. 22). 
When studied under a higher power the chseta appears to be triangular or possibly 
quadrangular in section (figs. 23, 24). Along two edges are ranged two series of spines 
or teeth, which decrease in size as they are traced downwards proximally. Each pair 
of teeth is connected across the “ front ” of the chasta by a finely-striated membrane 
or pectinated frill, the margin of which is comblike, as if it were made up of many very 
delicate chitinous hairs closely set side by side. In the more distal of these combs the 
hairs gradually increase in length, and beco ne flexible until the long hairs that form 
the “ beard ” are produced. Similar but less developed frills extend outwards beyond 
the teeth, down the “ sides ” of the chsetse, but in the proximal portion this lateral frill 
is replaced by a series of minute conical teeth (fig. 24). The spines or teeth are evidently 
merely specialisations of the comb-teeth. 
The shorter upper cheetse of the bundle have simple frills, but as the chsetee get 
longer the four or five of the distal frills become produced into the long hairs. There 
is quite a gradual transition between the chsetse with simple frills and those with well- 
developed beards.” 
These “ beards,” as Elders notes, entangle mud and debris, so that it is not 
always possible to obtain a good view of the apex and to make out the real structure, 
but in some of my mounts, both in Canada balsam and glycerine jeliy, the apices are 
fortunately free of mud and the structure is quite apparent. 
The ventral elicit 9e, too, are worthy of closer description than Elders has given 
them. They are quite different from those of II. spin os a, as he has shown. 
Each presents two parallel series of short stout teeth or spines along the concave 
edge, four or five in a series in the case of the longer chsetse, but reduced to three in the 
smaller ones (figs. 25-27). The more distal spines in each series are simple and tooth¬ 
like, but lower down each is seen to be surrounded at its base by a pectinated frill, or, 
lower still, to be replaced by a frill whose edge, under a low power, has the appearance 
of a tooth (fig. 27). These upper frills have quite a limited extent, but below them 
come four to six closely-set small frills of very short pectinations which run right across 
the chseta from side to side. 
The elytra on two of the individuals studied present marked variation from the 
typical structure. In addition to the characteristic sub-marginal papillae, the elytra bear 
conical and vesicular tubercles of brown colour. On the anterior elytra they are compara¬ 
tively small, lying on the uncovered posterior region of the scale, but on the more pos¬ 
teriorly situated elytra the tubercles become more conspicuous. They are here larger, 
though less numerous, till, on the last six or seven, they are truly enormous vesicles (fig. 
28). Whereas,the tenth elytron carries some half dozen of these vesicles, the fourteenth 
bears but one (fig. 29). These vesicles appear to be much enlarged and dilated tubercles 
derived from the ordinary eohinulate tubercles characteristic of the species. 
*83892—F 
