7<S 



a median tooth, which is well developed in Micrncreacjris Balz. (12. pi. 12 fig. 34 a) 

 and Ideoroncus Gracilis Balz. (12. pi. 12. fig. 31), but almost obsolete in Ideoblothrus 

 similis Balz. (lig. 32). Two, four or none eyes are present in the different forms. 

 The abdominal tergites are most often undivided; Ideoroncus laminatus n. sp. forms 

 an exception to this rule. The skin is smooth and the hairs are pointed; the 

 eleventh segment sometimes with real tactile hairs (cf p. 57). The antennae are of 

 moderate size in all forms, but Microcreagris Balz., which in size surpasses that of 

 all other Cbelonelhi (12. pi. 12, fig. 34); the flagellum varies from being fairly com- 

 plicated to being very simple. In Ideobisium crassimauum Balz, f inst. it consists 

 of seven, long pinnate hairs placed in a longitudinal row (49. tab. V, fig. 6) and 

 has most similarity to that of Obisiiim 111.; in Ideoroncus Siamensis n. sp. it is com- 

 posed of four, which are provided with a few teeth, while the number of the hairs 

 in /. Mexicanus Bks. is three, which are very short and almost simple (cf PI. I, 

 figs. 4-5 a, /; and 21. pi. IX, fig. 2 b). The lamina exterior is absent in all known 

 species but one, Ideoroncus laminatus n. sp. (PI. I, fig. 5 a, b); the serrula interior is 

 sometimes a real serrula as in Obisium 111. f inst. in Ideobisium crassimanum Balz. 

 (49. tab. V, fig. 6) and has sometimes the basal part more or less plate-shaped f. inst. 

 in Ideoroncus laminatus n. sp. (PI. I, fig. 5 a). The serrula exterior has in Ideoroncus 

 Mexicanus Bks. the distal third part free (21. pi. IX, fig. 2 c), while most other 

 species have the distal fifth portion or less free (PI. I, figs. 4 b); the teeth of Ihe 

 serrula are most often squarely truncate. The galea is generally similar to a 

 moderately curved stylet; Ideoblothrus Strandii Elling, and Microcreagris Balz, have 

 the galea divided into a few terminal branches; the galea is according to Banks 

 absent in the male of Ideoroncus obscurus Bks. (50. p. 11). 



The hindmost prolongation of the labrum is only short (PI. I, fig. 4c, p); the 

 laminae maxillares are fairly long and slender (figs. 4c-d, 5 b), and the lyriform 

 organs of Ihe maxillae attain at least sometimes a remarkable development (cf p. 28). 

 The shape of the palps is very variable, but does not provide characters of more 

 general interest; but the presence of tactile hairs on the dorsal and posterior sur- 

 face of the hand, is highly characteristic; similar hairs is only found in the 

 Chthoniidae Hans. The marginal teeth of the fingers of the palps are at least 

 generally poorly developed. The coxae are in all species, but one Ideoroncus 

 laminatus n. sp. placed on a lower level than the maxillae. The tibial femoral 

 part of Ihe first ])air of legs is rather short and similar to a tibia, but most often 

 more widened out than in Obisium III.; the articulate membrane of the trochantin 

 of the femur IV is generally a little oblique and the joint itself seldom longer than 

 one third of the whole femur, sometimes less. The tarsi of at least the first pair 

 of legs are always longer than the tibia, but not always to the same degree; 

 the tarsi of Ideoroncus Siamensis n. sp. f inst. are 17 longer than the tibia, while 

 those of /. laminatus n. sp. are 13 longer. The tarsi of the fourth pair of legs are 

 generally longer than the tibiae, but less so than those of the first pair of legs; 

 there is however one exception namely Ideobisium Balzanii With, in which the 



