;* 



MEGACOBMUS.— CENTETJEOIDES. 1 9 



tooth on its anterior border ; hand with six granular keels, the inner half of its upperside with two 

 granular finger-keels and one keel between them, its outer surface with a median keel ; width of hand 

 about two-thirds the length of the underhand, which is almost equal to the movable finger; the latter a 

 little shorter than the carapace, without lobe. Legs externally granular ; coxae thickly granular. 

 Pectinal teeth 4 ; shaft of pecten distinctly segmented, divided by two transverse sulci into an apical, 

 a median, and a basal sclerite, the latter divided by a longitudinal sulcus. 



Measurements in mm. — Total length 32, carapace 4*5, tail 16 ; width of first segment 2, of fifth 1*5, of 

 brachium 1-5, of hand 2*5 ; length of underhand 3*5, of movable finger 4. 



Hab. Mexico, Atoyac in Vera Cruz [A. Duges l ). 



Fam. BUTHmai. 



In all the known Central-American genera of this family the sternum of the cephalo- 

 thorax is triangular, its sides anteriorly converging ; there are two pedal spurs upon 

 the arthrodial membrane connecting the protarsus with the tarsus, and the anterior of 

 these is branched ; the two halves of the genital operculum are separated in both sexes 



■ 



and there is a single tooth upon the lower side of the immovable fang of the 

 mandible. 



Distribution. Tropical and temperate countries of Eastern and Western Hemispheres 

 to the south of 40°-45° of North latitude. 



Synopsis of the Central- American Genera. 



a. Dentition of the fingers of the chela consisting of series of median 



rows of teeth flanked by numerous small supernumerary teeth. 



a 1 . Tail not posteriorly expanded, longer in male than in female ; 



sternum of first abdominal somite scarcely sulcate . . , . • Centruroides, Marx. 

 b l . Tail posteriorly expanded, much thicker but scarcely longer in 



male than in female; first abdominal sternum strongly sulcate. Rhopalurus, Thor. 



b. Dentition of fingers of chelae consisting of median rows of teeth. 



a 2 . Rows of teeth on the fingers of the chelae not overlapping * . Isometrus, Hempr. & Ehr 

 b 2 . Rows of teeth on the fingers of the chelae largely overlapping . Tjtyus, C. Koch. 





CENTRUROIDES. 



(1828) 



Wiss 



t 



(1876) ; Atti Soc. Ital. Sci. Nat. xix. p. 83 (1877) ; Karsch, Mittheil. Munch, ent. Ver. iii. 

 p. 18 (1879) ; Pocock, Journ. Linn. Soc, Zool. xxiv. pp. 385, 391 (1893) ; Kraepelin, Jahrb. 



W 



Scorpiones et Pedipalpi, p. 87 (1899) 



(part.). 



1-48 (1815) (part.) [nee iii. p. 33 (1836)]. 



Nee Centrums, C. Koch, Die Arachn. iv. p. 110 (1838) ; Gervais, Ins. Apt. iii. p. 49 (1844). 

 Nee Centrums, Wood, Proc. Ac. Philad. 1863, p. Ill ; Journ. Ac. Philaci. (2) v. p. 372 (1863) 



- • 



Centruroides, Marx, Proc. U. S. Nat, Mus. 1889, p. 211. 



d2 





