AND AYES OF NORTH AMERICA. 



103 



Fig 30. 



In comparing this series with those of Poecilopleurum, 

 so well illustrated by Desloiigchamps, it is observable that 

 vertebra of similar proportions in the two are without diapo- 

 physes in the former, while they possess them in the latter. 

 Thus the diapophyses probably cease at a point in Laelaps 

 anterior to the same in Poecilopleurum. It is also noticeable 

 that while they are obliquely directed backwards in the latter, 

 those having them as well developed in the former exhibit 

 them transverse. 



Humerus. — Both are preserved, but lack the distal con- 

 dyle; about half the coronoid fossa of one remains, furnish- 

 ing an indication of the breadth of that extremity. They 

 are proximally much dilated, having a very strong postero- 

 external ala and a shorter antero-internal dilatation. They 

 are not half the length of the femur; the shaft is flattened 

 antero-internally. Of the proximal articulating surface a 

 portion is lost, but a narrow surface continuous with it exter- 

 nally does not extend further out on the dilatation than oppo- 

 site to the middle of the shaft. I find no trace of a globular 

 condyle, as is seen in Hadrosaurus. Coronoid fossa large and 

 well marked, not near to penetrating; medullary cavity of shaft 

 relatively smaller than in the bones of the leg. 



Length of humerus (restored), 

 Greatest proximal breadth, 

 Distal breadth across coronoid fossa, 

 Circumference of shaft, 



In. 

 12. 



3.75 



3. 



5.1 



These humeri are relatively shorter than in Hadrosaurus 

 and Iguanodon, and the external alse do not pass so abruptly 

 into the shaft as in them. They resemble most those of Poeci- 

 lopleurum. They differ from these in being much dilated dis- 

 tally, especially internally, and in having the coronoid fossa 

 much more pronounced. 



l&re-ttmb. — In the lack of the necessary pieces, one can- 

 not go far wrong in estimating the length after that of Poe- 

 cilopleurum. In it the lower arm is three-fifths the humerus, 

 which gives for Laelaps a length of 19.2 in. to the wrist. If 

 we accept the Crocodile as the next nearest ally in the fore- 

 limbs, we find the carpus and hand to be .75 of the humerus. 

 The ungueal phalange preserved in Poecilopleurum is shorter 

 than in the Crocodile; if however we add 9 inches to the 

 length already estimated, we have for the whole 2 ft. 4 - 2 

 inches. 



This is, as will be hereafter shown, a little more than one 

 fourth (1-3.71) the length of the hind limb. 



