32 ProcredingR nf the Royal Tn'sh Academy. 



should their presence or absence be regarded as of such moment, when species 

 with or without a post-antennal organ may be left peacefully side by side in 

 the same sub-family? And now, in his last paper ('13 J), Borner announces 

 the discovery, on the trochanters of the hind legs of Entomobryinae, of 

 another type of microscopical sense-organ. Since these are wanting in the 

 Isotomurini, he restores this group, although its members possess " both- 

 riotricha," to its natural position among the Isotominae. I am glad, tlierefore, 

 that before reading Borner's latest "system " I had decided to be unfashionable, 

 and to retain Isotomurus and its allies among the Isotominae, especially in 

 view of certain admissions previously made by Borner with regard to 

 Axelsonia, an allied genus of very great interest discussed below. 



Isotominae. 



Two species from the Seychelles are referable to this sub-family as just 

 defined, both belonging to the disputed group of the Isotomurini ; the typical 

 Isotomini are apparently absent from the fauna of the Archipelago. The 

 species represent two distinct genera which may be readily distinguished. 



A. Foot-claw with distinct basal filiform processes. Bothriotricha 



simple, ......... Axelsonia. 



B. Foot-claw without basal processes. Bothriotricha feathered, /soto»iM?-«5. 



Axelsonia Borner. 



This genus was diagnosed by Borner ('07, p. 1-17) for a marine species 

 found in barnacle-shells on the Manavara reef off' the coast of Madagascar. 

 He had, in the previous year ('06, p. 159), published the name, referring to 

 the genus in addition to the Malagasy species, Isotoma nitidci Folsom ('99 a, 

 p. i'G-i, figs. 14-18), from Japan. The slender claw-processes (fig. 12 l.p.) and 

 the simple bothriotricha on the al)dominal segments serve to distinguish most 

 defiuiteh' Axelsonia from all known Isotomine or Isi'tonnirine genera. 



Axelsonia thalassophila Borner. 



(Plate XIV, figs. 7-14.) 



Tins species was founded by 156rner (I.e., pp. 147-150, figs. 1-7,1 for 

 marine spring-tails collected in barnacle-shells on a reef in Antongil Bay 

 (east coast of Madagascar). The Axelsouiae of the Seychelles collection do 

 not appear to differ specifically from Borner's insects ; the oidy noteworthy 

 divergence is in the comparative lengths of the thml and fourth abdominal 

 segments, the former being distinctly the longer in the insects now recorded 



