162 MR. A. H. HALTDAT ON A NEW GENUS OF INSECTS. 



branch gives off a tuft of dark-coloured spines, generally covered 

 witli sordes, but when placed under tbe microscope are slender, 

 witb a smootb stalk, but finely denticulate for some way down 

 from tbe apex, on botb edges. The ventral branch is conical, 

 rather sharp pointed, and gives ofi" a tuft of yellow bristles. These 

 are longer and stronger than those of the dorsal branch, and are 

 strongly denticulate for some distance from the point. This va- 

 riety diifers from the typical form of cirratus in being altogether 

 broader in shape ; in being narrower at the anterior extremity 

 than the posterior, the reverse of which is the case in cirratus ; 

 and in the cirri not being swollen or enlarged a little below the 

 apex. 



It is found inhabiting the tube or case of living Ghcetopteri. Mr. 

 J. Williams, of Beaumaris, to whom I am indebted for the speci- 

 mens, finds them nearly constantly in the case of the Gh(Stopterus 

 insignis at low water. In his letter to me he says, " it is gene- 

 rally found crouching on the lower segments of the body of the 

 ClicBtopterus, and the earliest indication of the death of that an- 

 nelide is the exit of the parasite from the tube." 



Hah. Menai Straits, near Beaumaris. J. "Williams. (Mus. 

 Brit.) 



On Dicellura, a new genus of Insects belonging to the Stirps 

 TJiysanura, in the order Neur opera. By A. H. Halidat, A.M., 

 F.L.S. 



[Eead January 21, 1865.] 



The genus is founded on an undescribed insect allied to Gampodea 

 aonbulans, L. (sp. Foclura) in general appearance and habits," but 

 distinguished especially by having (in place of the pair of many- 

 jointed filaments which terminate the abdomen in that species) a 

 forceps like that which characterizes the Stirps LaUdura in the 

 same order. Dicellura solifuga appears to have a pretty extensive 

 range in latitude, having been found, firstly, by Mr. Lucas in 

 Algeria; afterwards at Paris, by the same author, who has re- 

 ceived it also from the neighbourhood of Toulon ; while the writer 

 has found it in diff"erent parts of Central and Southern Italy. 

 The institution of a family Dicelluridse is suggested to comprize 

 the two genera named, and distinguished from the remaining 

 circumscribed group of Lepismidce by the binary number of pos- 

 terior appendages, the exarticulate tarsus, the simply falcated 



