112 



THE EXTINCT BATKACHIA, REPTILIA 



In Laelaps it is shorter than in any known Dinosaur, measuring less than the hind limh 

 by a foot. It was cylindrical, slender towards the tip, and in fact not unlike that of a dog, 

 and probably capable; of motion similar to the latter. When the Laelaps stood erect, the 

 tail would trail its extremity on the ground, but could furnish little support. 



Comparison with oilier Dinosauria. — The species with which detailed comparison can 

 be made, are the Foecilopleurum bucklandii DeslongchampS, and Megalosaurus bucklandii 

 Mantell. All three were of nearly similar size. The Poecilopleurum is better known 

 than the Megalosaurus, and furnishes many similar parts. Thus the humeri possess the 

 the same disproportionately small size, the extremity of the tibia, is similarly expanded and 

 flattened, and is similarly embraced by the astragalus. There are, however, abundant 

 specific differences in all the bones described by Deslongchamps. In the same manner 

 the Laelaps aquilunguis presents abundant specific difference from the Megalosaurus buck- 

 landii. The slender, curved lemur (lifters from the massive; straight one of the hitter ; the 

 tibia is more slender, and more flattened distally; its extremity is wedge-shaped, not 

 rhombic as in European species. The claws of the Megalosaurus are relatively shorter 

 and less curved. 



The generic relations with these two types must be understood. Laelaps is obviously 

 distinct from Paecilopleurum in the structure of its feet. In the former the phalanges are 

 slender, in the latter massive, and mostly broad. The claws are more different ; in the 

 former compressed and hooked; as broad as deep in tin; latter, and but little curved. 

 They are prehensile in the former, in the latter not at all, or adapted only for defense; 

 they present a very small point of insertion, compared with the large knob of the former; 

 they also exhibit a deep groove on the side, which is weak in 'Laelaps. The difference 

 in this respect is about that between a, raptorial and rasorial bird. 



As compared with Megalosaurus, Laelaps probably had very short fore limbs. I have 

 pointed out the difference in the femur, which is perhaps no more than specific, though 

 this cannot be positively asserted. Tin; difference in tin; form of the extremity of the 

 tibia I suspect also to indicate more; than specific difference. The bone supposed by 

 Owen (Palacontographioal Society) to be scapula furnishes means of estimating the size of 

 the humerus. The glenoid cavity is some six inches in diameter, indicating a humerus 

 of four times the size of that of Laelaps at least. But this bone is more; likely to be an 

 ischium than scapula. The claws also of Megalosaurus are intermediate between those of 

 Laelaps and Poecilopleurum, being less compressed and hooked than in the first. 



Mze. — In estimating the length of this reptile we have the lengths of the limbs and 

 tail, and proportions of parts of the jaws to rely on. There is some reason to believe that 

 the lengths of the; hind leg and the tail we're similar. In erect animals, as the; Kangaroos 

 and Ostrich, the; length of the vertebral column anterior to the; sacrum about equals the 



