4 PROCEEDINGS OF THE NATIONAI. MUSEUM vol.73 



three species are known from the United States. Our two sub- 

 families and two genera may be separated as follows : 



KEY TO TUB SUBFAMILIES AND GENERA OF TUE FAMILY SCOKPIONIDAE OCCUEKING IN THH 



UNITED STATES 



A* No spine or tubercle under tlie sting on caudal vesicle. 



Subfamily Ischnurinae. 



Only a single genus represented in the United States. 



Opisthacanthus Peters. 



A'. A spine or tubercle under the sting near its base__Subfamily Diplocentrinae. 

 Only a single genus represented in the United States. 



Diplocentrus Peters. 



Genus OPISTHACANTHUS Peters 



In OpistJiacanthm the pedipalps are very large, and the post- 

 abdomen is reduced and compressed. The carapace is deeply emar- 

 ginate in front and has a median groove for the entire length. There 

 are three ocelli on each side. The tarsi have two ventral rows of 

 small spines. The pectines are short, with only a few teeth. 



Formerly this genus included species occurring in tropical Africa 

 and Madagascar as well as those found in tropical America. Now 

 the African species are placed in a distinct genus. We have but a 

 single representative, O. leftwrus Palisot de Beauvois, which has 

 been reported from Florida. Formerly this species was known as 

 O. elatus Gervais. The species occurs in Panama and the West 

 Indies. Records of its occurrence in Mexico appear to be wanting. 



Genus DIPLOCENTRUS Peters 



In Diplocentj^s the anterior margin of the carapace is deeply 

 emarginate; there are three ocelli on each side; and the ocular 

 tubercle is in front of the middle of the cephalothorax. The fingers 

 of the chelae are provided with a close-set longitudinal series of teeth 

 and a lateral series on each side of scattered teeth some being en- 

 larged. The fifth segment of the postabdomen has a ventral semi- 

 circular area bounded by a row of granules. The sting is provided 

 with a basal tubercular tooth. 



The genus is found throughout most of tropical America. Dr. 

 de Mello Campos (1924) records a single species from Brazil. Three 

 species occur in the United States, two in the Southwest and one in 

 Florida. The southwestern species may be separated as follows: 



KEY TO THE WESTEKN UNITED STATES SPECIES OF DIPLOCENTRUS 



Color very dark reddish brown, almost black ; length from 5 to 7 cm. ; pectinal 

 teeth 14 ^- ^^"^^ (Gervais). 



Color reddish brown but not approaching black; length from 4 to 5.5 cm.; pec- 

 tinal teeth 9-11 ». keyserlingi Karsch. 



