ARTHEOPOD PAUNA OF TUE WEST I^^DIES. 385 



of the posterior segments are densely aud coarsely granular; 

 the vesicle ovate, sparsely granular, almost as wide as the fiftk 

 segment (2*5 mm. : 3). with a small thick tooth beneath the long 

 aculeus. 



PaZpi with hands equal in width to the brachium ; the movable 

 digit a little less than twice the length of the hand-back, scarcely 

 lobate, with 14 rows of teeth. 



Pectines with 17 teeth. 



Total length 53 mm., of carapace 5'7, of tail 34, width of tail 3, 

 length of fifth segment 6 2. 



Of the preceding species T. antillanus, in having the tail pos- 

 teriorly coarsely and closely granular, its keels denticulate, and 

 the superior lateral margins of the fifth segment sharp, approaches 

 apparently most nearly to T. ohtusus of Karsch, which it further 

 resembles in having a wide caudal vesicle, a small tooth beneath 

 the aculeus, and the same number of pectinal teeth. But never 

 having seen tlie female of T. ohtusus, I do not feel justified in 

 making the two synonymous. 



Genus Ceintteuiius {Hempr. Sf Ehrh.), Thorell. 

 Synopsis of the Species q/" Centrums. 



a. The 2nd and 3rd caudal segments furnished with 



1 keels princeps, Karsch; 



b. The 2nd and 3rd caudal segments furnished with 



only 8 keels. 



a^. A distinct spine beneath the aculeus of the 



poison-vesicle ; the pectinal teeth on an 



average 30 (25-35). 



d'. With 9 rows of teeth on the digit of the 



palp ; hand thinner, granulation finer, 



colour darker gracilis (Latr.). 



b^. With 8 rows of teeth on the digit of the 



palp ; hand thicker, granulation coarser, [(Gerv.). 



colour redder margaritatus 



b^. With only a minute tubercle beneath the 



aculeus of the vesicle ; pectinal teeth fewer 



than 25. 



a^. Hand wider, its width in the adult more 



than half the length of the movable digit ; 



tail smoother, shining nitidus, Thor. 



b^. Hand narrower, its width about one third 

 the length of the movable digit. 

 a^. Tail much thinner; trunk a uniform tint 



above and more coarsely granular testaceus (De Geer). 



