Collembola.] SUBANTARCTIC ISLANDS OP NEW ZEALAND. 379 



The above diagnosis serves to distinguish the Campbell Island springtail from 

 other species of the genus. As there is abundant material, I have studied the struc- 

 ture of the insect, especially the jaws, in some detail, and the following features 

 seem worthy of notice, as the genus is as yet very imperfectly known : — 



Ocelli and Sense-organs. — The arrangement of the ocelli seems much the same 

 in this species as in Triacanthdla rosea, Wahlgren, and Triacanthurus davatus, Willem, 

 both of which have the corresponding 2 of each 8 very small ; in T. michaelseni, 

 Schaeffer, only 1 (the anterior of the corresponding 2) is reduced. Each ocellus has 

 a distinct black pigment spot beneath it, so that the arrangement of the ocelli stands 

 out clearly on the white ground-colour of the head (fig. 1). The post-antennal organ 

 is somewhat like that of T. rosea as figured by Wahlgren (1906, fig. 11): usually 

 there are 4 elongate prominences (fig. 4), but these structures vary both in number 

 and form ; in one specimen the right post-antennal organ has only 3 prominences 

 (fig. 2), while the left has 5 (fig. 3). 



The antennal organ at the extremity of the 4th segment (fig. 6) consists of a large 

 subglobular prominence, with 2 adjacent swellings of the cuticle. At the distal end 

 of the 3rd antennal segment on the outer dorsal aspect there is a sense-organ con- 

 sisting of 2 short stout peg-like bristles, each with a distinct longitudinal groove 

 (figs. 2, 5). 



Jaws. — The mandibles (figs. 8, 9) are of the typical collembolar form ; each 

 bears, however, 2 remarkably prominent teeth at the proximal end of its molar 

 area, on the inner anterior aspect. The maxillulae occupy the usual position with 

 regard to the tongue (fig. 10, a, b) ; each maxillula is delicate, but strengthened 

 with various chitinous thickenings, and the teeth along the inner proximal border 

 are relatively stout. Little doubt can be entertained that these structures are a pair 

 of appendages (between the mandibles and maxillae) which become reduced or 

 absent in winged insects. 



Each maxilla (fig. 10, c, 11) has the cardo (cr) in its usual relative position to 

 the stipes (st) outwardly, and the chitinors foot (pe) of the tongue inwardly. In the 

 head of the maxilla the 2 hinder lamellae (la') are remarkable for their excessive 

 length, as they project far beyond the stout two-toothed outer process (h) of the 

 maxillary " head." The 2 anterior (dorsal) lamellae (la) are of normal appearance. 

 The structure usually known as the " maxillary palp," which Borner (1908) has 

 recently homologised, for the most part, with the outer coxal segment and the galea 

 of the thysanuran maxilla, resembles closely that of an Achorutes, having a tubercu- 

 late process (the palp proper, according to Borner), with a long bristle at its tip and 

 another near its base, while the distal end of the structure is acuminate. 



From my own studies of Collemhola I believe it at least as likely that this so- 

 called " palp " belongs to the maxillulae as to the maxillae ; both Stummer-Traunfels 

 (1891) and Hansen (1893) refer it positively to the former appendages. In the 

 present genus its inner basal edge is attached to the base of the maxillula, its outer 

 to the stipes of the maxilla (fig. 10). 



The labium (fig. 12) consists of the usual paired sclerites forming the mentum, 

 fused with the ventral head-skeleton ; and a pair of lobes, each of which has 6 bristle- 

 bearing papillae. 



Legs. — The foot of Triacanthdla alba (fig. 13) is interesting on account of the 

 vestigial empodial appendix (" inferior claw "). The two Fuegian species referred 



