1890. J OF THE FAMILY BUTHID-E. 119 



is, in my opinion, very much to be deprecated, I have added Tityus 

 to the synonyms oUsometrus, and have taken Peters's name Vroplectes 

 for the species which Thorell called Tityus. This, however, J. have 

 done on tlie authority of Dr. Karsch, who in a footnote to his table 

 of genera says that Uioplectes is synonymous with Titi/us in Dr. 

 Thorell's sense of the word. Presumably this statement is made 

 after an examination of the type of Uroplectes, namely U. ornatus. 

 If this, however, be not so, it will be well to bear in mind that there 

 is nothing in Peters's diagnosis of ornatus to show that the species is 

 not referable to Lepreus. In that case Lepreus will have to rank as 

 a synonym of Uroplectes, and a new generic name will have to be 

 established for the species here included under Uroplectes, unless the 

 alternative lie adoj)ted of considering all the species of Lepreus and 

 Uroplectes as referable to one genus Uroplectes \ 



Genus Isometrus, Ehrb. 



Isometrus, Ehrenberg, Symb. Phys. (Scor[)iones), p. 3, pi. i. fig. 3 

 (1829) — type Jilum=^maculatiis (De Geer). 



Tityus, C.Koch, Die Arach. lii. p. 33 (1836) — type bahiensis {Perty). 



Pilunmus, id. Arach. Syst. p. 38 (1837) (nom. prseocc). 



Lychas, id. Die Arach. xii. p. 1 (1845) — type ynaculatus (De Geer). 



Atreus, Gerv. Apt. iii. p. 52 (1844) (in part), not of C. Koch, 1837, 



Centrums, Peters, Monatsb. Ak. Wiss. Berlin, 1862, p. 512 (in 

 part). 



Isometrus, Thorell, Etudes Scorpiol. p. 9 (1876) (and subsequent 

 authors). 



Phassus, id. ibid. 



Androcottus, Karsch, Mitth. Miinch. ent, Ver. p. 1 1 (1879). 



Sab. Tropical countries. 



Inferior border of the immorable digit of the chelicerfe armed 

 with a single tooth. 



The external series of teeth on the digits of the chelae formed by 

 the assumption of a more or less transverse position of the posterior 

 one or two enlarged teeth of the median rows ; the internal 

 series of teeth formed by the enlargement and separation of the 

 anterior tooth of each of the median rows ; but this separation is 

 never carried to any great extent. In most of the Old-World species 

 the median rows scarcely overlap each other ; but in the larger 

 American forms, such as I. androcottoicles, the rows overlap to 

 such a degree that the anterior extremity of any one reaches the 

 middle of the row in front of it. 



The cephalothorax is usually without well-developed keels ; the 

 tergites are nearly always provided only with a median keel ; the 

 tail is, as a rule, keeled above and below, and the vesicle is nearly 

 always provided with a strong spine beneath the aculeus. 



The sexes generally differ considerably and in a variety of ways : 

 thus the male oil. messor and of i. maculatus has long chelte with 

 slender hands and a long tail ;. I. tricarinatus has short chelae with 

 thick hands and a long tail ; I. muci-onatus (varius) has a thick hand 



* I ha-ve refrained from definitely uniting the two genera, because ^Ji7os«s 

 the type of Lepreus, is unknown to me. 



