34 Proceedings of the Royal Irish Academy. 



Isotomursus Bonier. 



This genus was founded by Bonier ('03, p. 171) for the common European 

 Isotoma palustris (Miiller), and no other species seems as yet to liave been 

 included in it. Members of the genus resemble the typical Isotomiiii in all 

 important points of external structure, but are distinguished by the presence 

 of the six pairs of bothriotricha already mentioned on the abdominal segments. 

 If we are justified in regarding the possession of these as an archaic character, 

 it is of especial interest to find that Isotomurus is represented in the fauna of 

 the Seychelles. 



Isotomurus obscurus sp. nov. 



(Plate XIV, figs. 15-19.) 



Feelers half as long again as the head (fig. 15); relative length of 

 segments as 3:8:10: 11. Ocelli eight on each side, the inner posterior one 

 markedly smaller than the rest ; post-autennal organ broadly ovate, only 

 slightly longer than the diameter of an anterior ocellus (fig. 16). Foot with 

 simple, untoothed claw and lamellate acuminate empodial appendage ; no 

 tenent hair (fig. 17). Length of third and fourth abdominal segments 

 equal ; fifth and sixtli abdominal segments distinct, and bearing a few long 

 bristles. Spring somewhat short and stout ; dens half as long again as 

 maiHibriuni, tapering rapidly to tip ; niucro (fig. 19) with prominent apical 

 and dorsal teeth, and a minute accessory dorsal tooth. 



Length 1'75 mm. Colour deep violet-blue, except for the sutures of the 

 body-segments and the dens and mucro, which are white. 



Localities. — Silhouette, 1908 (6 specimens). Mah6: Foret Noire, 1000 ft., 

 190S [2 specimens). 



I'his species is closely allied to the European /.p«/!(6'<m (Miiller), but the 

 latter has a tooth on the empodial appendage of the foot, and a small ventral 

 tooth on the mucro of the spring. Its post-antennal organ also differs from 

 that of the Seychelles species, being narrowly elliptical. /. palustris has been 

 recorded from Java by Borner ('06, p. 173) and from Calcutta by Imms 

 (12, p. 93). 



Entomobryinae. 



From tlie number of species included in this sub-family, it may be regarded 

 as the dominant group among the Seychelles Collembola. Borner and other 

 systematists recognize several tribes which may be regarded as natural 

 assemblages of genera, and are at least convenient for purposes of classifica- 



