ON TRACHEAN ARACHNIDA. 519 



Illiger, in a table, merely nomenclatoiy of the genera of 

 the class insecta, which he has placed at the end of his work 

 on the Coleoptera of Prussia, separates from the scorpions the 

 species which Fabricius names cancro'ides, and cimico'ides, to 

 form a particular genus, which he calls ohisium, and which 

 corresponds exactly with the chelifer of M. Latreille in his 

 Summary of the generic characters of insects, published 

 anteriorly to the work of M. Illiger. Dr. Leach, adding 

 some new observations to the preceding, has preserved the 

 genus ohisium of Illiger, but restrains it to the genera of 

 cheliferi, which have four simple eyes, the body almost cylin- 

 drical, and the eight posterior feet composed of six articula- 

 tions. The species in which the feet have but five articula- 

 tions, whose body is depressed, and presents but two simple 

 eyes alone, form the genus chelifer, of this gentleman. {Zool. 

 Miscell. vol. iii. p. 48.) He places these two genera in the 

 family of the scorptoiiidea. 



Although it cannot be denied that these arachnida have, in 

 their general structure, a great resemblance to the scorpions, 

 they appear, nevertheless, to differ from them in some anato- 

 mical considerations. They present but two stigmata, situated, 

 one on each side, above the origin of the two anterior feet. 

 M. Latreille has, therefore, placed this genus, in his family of 

 Pseudo-scorpiones, which immediately succeed that of the 

 scorpiooiides. If it be true, that M. Fischer has observed in 

 these animals, and the galeodes, respiratory organs, similar to 

 those of the araneides, the family of false scorpions, composed 

 of these two genera, should naturally terminate the order of 

 pulmonary arachnida. 



The cheliferi have the body ovoid and depressed, or oblong, 

 and almost cylindrical, invested with a dermis somewhat 

 coriaceous, almost smooth, or but slightly furnished with 

 hairs. It is composed, 1st. of an anterior segment much the 



