No. 598] 



THE STERNUM LX SCORPIONS 



COT 



is taken from my monograph and represents the holotype 

 of Eoscorpius 1 intuits ;is it appears on the reverse. Fig. 

 3 is a careful drawing of a very young ('cut runts in fount- 

 his made with the aid of an Abbe apparatus. This figure 

 is much more enlarged than is Fig. 4, to facilitate com- 

 parison. The shape of the ahdonien, as is well known, 

 is the least constant character and we will leave it out of 

 consideration. To avoid criticism, however, I would state 

 that the great distension of the abdomen in the voung 

 Centrums is due to the presence of embryonic volk. 

 When this disappears, the abdomen becomes much thin- 

 ner. In older specimens the distension of the abdomen 

 is frequently due to the growing embryos. Yet, in dis- 

 secting what I supposed to be gravid females, I was sur- 

 prised to find no embryos in them and only small ovaries. 

 The fact is that the distension of the abdomen is also often 

 due to the condition of the liver. 



cause the carapace of Vejovis, except for its size, is also 

 of similar shape. The rows of granules on the caudal 

 segments are not sufficiently well preserved in the fossil 

 specimens to allow of a conclusion as to their exact num- 

 ber. On the other hand, the transverse row of granules 

 at the anterior end of the first caudal segment, present in 

 Eoscorpius and wanting in the adult Centrums, is clearly 

 defined in the young. The most interesting character is 

 represented in the hand with its fingers. As a rule the 

 ratio between the length of the fingers and that of the 

 hand is a fairly constant one for each species. In the 

 holotype of Eoscorpius typicus it is approximately 2:1; 

 in the adult Centrums mfamatus it is 1.6:1, but in the 



2:1. With other words, Cmlntnts developed from an 

 ancestor with relatively longer fingers and the trend of 

 evolution was toward reduction in their length. 



One character presents a difficulty. This is the comb. 



