10 TERRESTRIAL CARBONIFEROUS ARACHNIDA. 



with Mr. Holt's example in the mode of attachment of the coxae in question ; but 

 even if in these specimens the sclerites on each side of the genital operculum do 

 not, as figured by Fritsch, belong to the fourth leg, the presence of sclerites on each 

 side of this plate is a feature unknown in modern Scorpions, where the operculum 

 is the sole trace of appendages of the first segment of the opisthosoma. These 

 sclerites, therefore, are of great morphological interest, whatever interpretation be 

 put upon them. It is possible, indeed, that they must be compared with the 

 lateral plates of the genital segment present apparently in the Silurian Scorpion I 

 described as Palseoplionus hunteri 1 (Quart. Journ. Micr. Sci., 1902, p. 291, pi. 19). 



The peculiarities above described do not, however, exist in all Carboniferous 

 Scorpions. In one of the specimens described below under the heading AutJiraco- 

 scorpio buthiformis the sternum of the prosoma, the coxas of the third and fourth 

 legs, and the genital operculum appear to be in structural agreement with the same 

 pieces in recent Scorpions ; and there is no evidence that they are differently 

 arranged in the example in the British Museum which I identify as Anthracoscorpio 

 sparthensis. The species described by Peach as Eoscorpins euglyptus and gin her 

 also seem to fall into line with recent types in the particulars named ; and 

 Fritsch's figure of G ' ijcloplithalmus senior is susceptible of the same interpretation. 



Hence it seems that the Carboniferous Scorpions are divisible into two groups, 

 one of which is inseparable on broad structural lines from recent species. The 

 terms " Anthracoscorpii " and " Neoscorpii " cease, therefore, to be applicable. 

 Although it is impossible to assign all the described Carboniferous species to one 

 or the other of these groups, it appears to me that the characters by which the 

 two are distinguished are too important and interesting to be ignored in a classi- 

 fication of this order. I propose, therefore, the term Lobosterni for those with 

 bilobed, posteriorlydaminate sternal plates on the opisthosoma and skeletal plates, 

 whether belonging to the fourth leg or not, on each side of the genital operculum; 

 and the term Orthosterni for those agreeing apparently with recent Scorpions in 

 the structure of the plates in question. In this monograph Eobuthus belongs to 

 the Lobosterni, and Cyclophthalmus, Archseoetomts and AuthracoscorpAo to the 

 Orthosterni, Palseomaclius being of doubtful position. Of exotic genera, Microlnbis 

 seems to be referable to the Orthosterni, Isobuthus to the Lobosterni, while 

 Eoscorpius and Mazonvi cannot be classified. Probably a special group should be 

 created for Mazonia if the extant restoration of the genus be accurate. 



The determination of the genera has been a matter of great difficulty, because 

 I have been compelled to rely mostly upon the figures and descriptions published 

 by Fritsch, whose acquaintance with the morphology of recent Scorpions is 



1 According to Mr. R. Dunlop (Ann. Glenfielcl Rambler, No. 2, 1898, pp. 60—64) this Silurian 

 Scorpion was named Palceoplwnus caledonicus by Dr. Peach. I do not know where Dr. Peach described 

 it under that name ; and possibly Mr. Dunlop, writing from me.nory, has confused this species with 

 Qlyjptoscorpius caledotiiciis. Provisionally, therefore, I retain hunteri as the specific designation. 



