608 



THE AMERICAN NATURALIST 



[Vol.L 



Specimen No. 37987 of the U. S. Nat. Mus. of Eoscorpius 

 shows a comb which is very broad at the base, and has, 

 apparently, a single median plate, a beadlike .inner row 

 and 19 teeth. I identified this specimen as Eoscorpius 

 typicus for the reason that "the general appearance of 

 the specimen, the shape "of the tergites, especially of the 

 seventh," strongly resembled the holotype. The speci- 

 men is incomplete and about twice as large as the holo- 

 type. Perhaps No. 37987 is after all of a different spe- 

 cies. The shape of the comb in recent species of Cen- 

 trums is not always the same as in infamatus. The comb 

 in C. junceus and C. agamemnon is twice as wide at the 

 base as in the middle. 



Taking all characters and the geographic distribution 

 into account, we can not fail to notice the greater simi- 

 larity between the young of Centrums infamatus and 

 Eoscorpius typicus than between the latter species and 

 Vejovis. What advantage, if any, Centrums has derived 

 from the shortening of the fingers and the change in the 

 shape of the sternum, is a totally different question which 

 may possibly be answered by studying the functions and 

 uses of these organs in recent species. 



