ON" SOME LlTILE-KNOWN COLLEMBOLA. 19 



ling hybrids, the progeny of a male Salmo solar and a female Loch- 

 leven troub. The interesting and practical question arises, Will 

 these, as a rule, be sterile or prolific ? I£ sterile, will they possess 

 the migratory instinct of the salmon or the non-migratory habits of 

 the brook-trout. Should the latter occur, rivers, such as the 

 Thames, might be stocked with fish suitable for sport and food 

 above the polluted portion. Theo, again, would arise the inquiry 

 whether they would remain in condition all the year round ; for 

 if so, such stock might afford constant sport to the angler, while 

 the captures would be clean fish. 



Notes on some little-known Coliembola, and on the British 

 Species of the Q-enus Tomocerus. By GtEoege Bkook, 

 F.L.S. 



[Eeacl December 7, 1882.] 



(Plate I.) 



The four species which form the subject of the present notes 

 have all been described by Tullberg. Dr. Eeuter has come 

 across a single specimen of Tomocerus vulgaris in Shetland, and 

 also a single specimen, which he queries Achorutes manubrialis, 

 from Finland. With these two exceptions I am not aware that 

 any of them have been since observed. Tullberg's specimens 

 were from Sweden, so that notes of their occurrence in England 

 and in Jersey may prove of value. When quoting Tallberg I 

 have made use of his latest descriptions, as these are iu some 

 cases altered a little from the originals. 



ACIIOEUTES MAIfUBRIALIS, TuUb. (PL I. figS, 1-5.) 



In October 1880, while on a dredging-trip wi,th Dr. Murie, we 

 lauded one day on Warden Point, Thanet, and began 'searching 

 the sun-dried blocks of clay on the beach. Amongst the crevices 

 of one large block Ifou.nd swarms of 2.^ Achorutes, which appeared 

 at first sight to be A. pur^urescens, Lubbock ; but a closer inspec- 

 tion made this doubtful, and we collected a good many for refer- 

 ence. Twelve months passed over without the specimens being 

 examined ; but when at last they were brought out, they proved 

 to be A. mamihrialis, Tullb., and an addition to our fauna. 



Tullberg's description is as follows : — " Uuguiculus inferior ad- 

 est. Dentes furculse, manubrio breviores, vix duplo longiores 

 quam mucrones, qui graciles sunt. Spinse anales perparvse, 



2* 



