175 

 Platyarthrus Hoffmannseggi, Brandt. 



(PI. LXXVI, fig. 2.) 

 Platyarfhnis Hoffmannseggi, Branch, Consp. monogr. Crust. Onisc. p. 12, PI. 4. fig. 10. 



Syn : Itea crassicornis, Koch. 

 Jyphloniscus Steinii, Schobl. 



Specific Characters. - Body broadly oval, and much depressed, with the 

 dorsal face smooth, though slightly granulose all over. Cephalon partly flanked 

 by the side-plates of 1 st segment of mesosome, frontal edge arcuate and minutely 

 crenulated, lateral lobes narrowly rounded at the tip, and obliquely produced in 

 front, edges crenulated. Side-plates of mesosome rather large, lamellar, sub- 

 contiguous, 1st pair the largest, edges finely denticulate. Metasome scarcely ex- 

 ceeding '/a f the length of the mesosome, the 2 anterior segments very small, 

 epimeral plates of the 3 succeeding segments narrow, recurved ; last segment 

 comparatively short, triangular, resembling that in Philuscia muscorum. Anten- 

 nulse with the basal joint fully as long as the other 2 combined. Antennae 

 scarcely exceeding } / s of the length of the body, and hirsute all over with short 

 hairs; last peduncular joint very large and dilated, flagellum shorter than that 

 joint, and lanceolate in form. Legs densely spinous inside, propodal joint coni- 

 cal in form. Uropoda with the basal part rather large, oblong, outer ramus 

 about same length and lanceolate in form, inner ramus much narrower, and 

 scarcely extending to the middle of the outer. Colour pure white. Length of 

 adult female 3 mm. 



Remarks. This peculiar Oniscid was first described under the above 

 name by Brandt. It was subsequently observed by Schobl, who regarded it as 

 new, and described it as Typhlonisc.us Steinii. Koch too does not seems to have 

 been aware of Brandt's description, and hence recorded it under another name, 

 viz., Itea crassicornis, referring it wrongly to his genus Jtea, which is identical 

 with Trichoniscus of Brandt. It is an easily recognizable Oniscoid, being easily 

 distinguished by its pale, flat body, the strongly built antenna?, and the total ab- 

 sence of visual organs. 



Occurrence. In Norway this form has not yet been observed; but, as it 

 is widely distributed over the northern part of Europa, I cannot doubt that, on 

 a closer investigation, it will be found to exist in this country also. Its pe- 

 culiar habits and occurrence within ants' nests may also be the cause of its having 

 hitherto escaped the attention of Norwegian zoologists. The figures here given 

 are from specimens kindly sent to me from the Zoological Museum in Copenhagen. 



Distribution. Denmark, Germany Holland, Britain, France, Bohemia, 

 Austria, Tyrol, Helvetia. 



