438 PROF. C. CHILTON ON DETO, A SUBANTARCTIC 



of the new species Deto armataf he gave an amended diagnosis, the main 

 characters o£ wliich are included in the following diagnosis which I now 

 suggest : — 



Generic diagnosis. — General shape o£ body oblong-oval, somewhat de- 

 pressed; animal not capable o£ rolling itself into a ball; epimera lamellarly 

 expanded * ; dorsal surface usually with spines or tubercles which are better 

 developed in the male than in the female ; pleon not abruptly narrower than 

 perseon ; epimera of third, fourth, and fifth segments well developed. Head 

 with lateral processes forming broad lobes. 



Eyes of moderate size, with many ocelli. 



Antennse with ilagellum four-jointed. 



Mandibles with one penicil behind the cutting-edge. 



Maxillipeds with palp longer than masticatory lobe, and showing indi- 

 cations of being formed of three or four joints. 



Exopoda of the pleopoda opercular, and containing no special branchial 

 organ. 



Uropoda produced, reaching considerably beyond the terminal segment. 



In addition to the points given above, there are several characters common 

 to these species which may be mentioned here to avoid repetition. 



Sexual dimorphism is very marked and affects the surface of the body and 

 the antennse, but not the perteopoda or uropoda, which are the parts that 

 usually show sexual differences in Trichoniscus, Poreellio, &c. 



The antennae are long and stout, usually stouter in the male than in 

 the female. 



The mouth-parts are on the same general type of those of Onisciis, and are 

 fairly uniform throughout the genus. I have described them in greater 

 detail for D. aiicklandice and I), huccideida, but a few points may be given 

 here. 



The mandibles are strong ; the accessory appendage differs on the two 

 sides, in the left mandible being formed of two or three strongly chitinised 

 teeth similar to the outer cuttino-edoe, in the right it is shorter and ends 

 in a crown of small teeth of varying sizes ; at the base of the accessory 

 appendage in both mandibles is a hairy lappet which may bear one or two 

 stout setse or " penicils '■* similar to the single penicil between the lappet and 

 the tuft of long bristles representing the molar tubercle. 



The lower lip consists of two rounded lobes separated apparently to the 

 base, but connected proximally by the inner more membranous lobes which 

 appear capable of being folded together at right angles to the lip, and when 



* la the female of Deto aucklandice the epimera of segments 2, 3, and 4 of the perason 

 are separated from their segments by a slight groove or apparent suture ; in the males of 

 this species and in both sexes of the other species the epimera are quite continuous with 

 their segments, the junction not being marked by any gi'oove or suture. 



