10 H. J. HANSEN. 



side (PI. 4, fig. 4 h) of tlie tliickoned joints are very elongate 

 and vertical on the antennal axis. In most species these setse 

 are slender, slightly conical, and naked, Imt in two species 

 of Scolopendrella (Scut, microcolpa, Mulir, and Scut, 

 antennata, n. sp.) nearly all the setaj are much thicker and 

 adorned with very conspicuous branches on all sides (PL 5, fig. 

 4 h, and PI. 7, figs. G a— 6 c). In all species at least one secon- 

 dary whorl of shorter setaG has been partly or fully developed 

 behind the central one, at all events in the inost distal joints. 

 In most species of Scutigerella and some species of Scolopen- 

 drella a third whorl is developed behind the second one or 

 between this and the central one, at least on the lower side of 

 the distal joints, and a rudiment of a fourth can sometimes be 

 found. On the upper side of the distal joints a part or a 

 rudiment of a whorl of fine and short liairs or seta) is found 

 in advance of the central one. The degree of development of 

 the whorls on the proximal, middle, and distal parts of tlie 

 antenna9 present specific characters. 



In Scutigerella I have discovered various sense-organs on 

 the antennae. In all species the terminal joint has on its 

 distal surface at least one organ — generally two or tliree 

 organs, — and these differ often, but not always, considerably 

 in size. An organ of this kind consists of a stalk which is 

 either short or rather long-, often gradually increasing in thick- 

 ness outwards, and from its end originate four fine branches 

 which are slightly convex outwards, subparallel or slightly 

 diverging, and certainly always united by a very thin, clear 

 membrane. A large organ of this kind, a striped organ, 

 placed on awart-like protuberance in Scut, unguiculata, is 

 shown in PI. 2, fig. 2 c; fig. 2 h on PI. 4 (in Scut, angu- 

 losa) shows a large organ and a smaller one with the branches 

 feebly developed. Fig. 2 h on PI. 5 represents the terniinnl 

 joint of Scut, paupcrata Avith two organs (moi-e magnilied 

 in fig. 2 c), one with branches in the membrane, the other 

 thicker, more rounded, without separate stalk, and without 

 branches. Fig. 2 h on PI. 4 shows not only two strij)ed 

 organs, but between the normal setae subcylindrical rods, 



