LITTLE-KNOWjSr COLLEMBOLA, 21. 



mucrones that it is almost impossible to saj' where the exact point 

 of iiuion is. In AcJiorutes, on the contrary, the contour of each 

 segment of the spring is well marked ; for even in A.purimresccns, 

 Lubbock, although the dentes gradually taper into the mucrones, 

 there is a distinct line across marking the point of union. In 

 JCenylla there is no lower claw, and the number of ocelli on each 

 side is five iustead of eight as in AcJiorutes. There are always 

 two tenent hairs on each tibia ; I have seea three in one or two 

 instances. 



-Z". marifima, Tullb., is distinguished as follows : — " Undique 

 pruuosa. Dentes furculae cum mucrouibus longitudinem tibiae 

 8ec[uautes. Spina) anales parvae, papillis latis affixee. Long, 

 1| mm." * 



This species is distinguished from the others of the genus by 

 its larger spring, with more suddenly tapering dentes, and by the 

 j)osition of the extremely small anal spines, which are j)laced on 

 two broad papillae toucMiig at the base ; while in X. hrevicauda 

 and X. niticla the anal spines are placed on papillae only slightly 

 larger than the granulations of the skin and with their bases 

 comparatively wide apart. My specimens were sent to me by 

 Mr. J. Sinel of Jersey, who collected them in Dec. 1881 under 

 damp wood, curiously enough in the company of Tomocerus 

 vulgaris, Tullb., about which I shall have something to say later. 



Tet^sna mirabilis, Tullb. (PI. I. figs. 11-14.) 

 Tullberg's diagnosis of this genus is as follows :— " Organa 

 postantennalia nulla; ocelli 16, 8 in utroque latere capitis. 

 Antennae conicae, articulo quarto gracillimo. Unguiculus inferior 

 nuUus. Purcula perparva, dentibus papilliformibus. Spingg 

 anales 3 "f. 



This genus, which contains as yet only one species, is nearest 

 related to Aiiurida of Laboulbene, which it resembles greatly in 

 the mouth-parts. These present a transitional stage between 

 Lijpura, in which the mandibles have a certain limited freedom 

 of action, and Anoura, in which the mouth is entirely suctorial. 

 Besides the three anal spines and the absence of a postantenual 

 organ, the chief characteristic of Tricena lies in the formation of 

 ^he spring. This is the most rudimentary one yet described, 

 and merely consists of a small basal piece and of two almost 



* Sveriges PoclLiricler, 1872, 

 t Ibid. 



