NATURAL SCIENCES OF PHILADELPHIA. 279 



That such a habit characterized the Laelaps is very probable ; the tail 

 was nearly cylindric, and from the extent of the condyles of the femur, the 

 hind limb must have been considerably flexed. The small size of the fore 

 limbs must have rendered them far less efficient as weapons than the hind 

 feet, in an attack on such a creature as Hadrosaurus ; hence perhaps the 

 latter were preferred in inflicting fatal wounds. The exceedingly eagle-like 

 character of the digits and claws and ornithic type of sacrum elucidated by 

 Prof. Owen, suggest a resemblance in the use of the limb. 



The bulk of the species, as compared with that of Hadrosaurus, illustrates 

 again the law observed in the relation between Felis and Bos, Thylacoleo 

 and the herbivorous implacentals of its time, and the other raptorial and 

 herbivorous Dinosauria, which might probably be reduced to exact terms. 



The remains indicate an animal of near 18 feet in length, which could pro- 

 bably raise itself to a height of six feet at the rump 



To recapitulate ; the genus Laelaps belongs to the family Dinodontidse, 

 which is characterized by its contractile raptorial claws and slender digits. 

 aDd compressed sabre-shaped teeth. It differs from Megalosaurus in its femur 

 and from Dinodon in that teeth of the latter have two posterior serrate 

 edges separated by a posterior plane. From supposed Dinosaurian genera of 

 doubtful affinity, it differs e.g. from Regnosaurus Mant. in the totally different 

 humerus, and from Pelorosaurus and Streptospondylus in the vertebrae. Ce- 

 tiosaurus and Cimoliasaurus were perhaps mutilate like the Cetaceans, accord- 

 ing to Owen and Leidy. 



In connection with the same fossil were found Cucullaea and Baculites sp., 

 and not more than twenty feet off a femur of Hadrosaurus ; also portions of 

 Mosasaurus, Hyposaurus, Thoracosaurus and Bottosaurus, occurred in the 

 neighborhood. 



The phalanges figured by Prof. Leidy (Smithsonian Contributions xii.) 

 Cretaceous Reptiles, Tab. 17, fig. 8 11, probably belong to the present species. 

 They are included under the head of animals allied to Hadrosaurus. 



In conclusion, the thanks of scientific men are due to Superintendent Voor- 

 hees for the interest and care evinced in the preservation of these valuable 

 specimens. Were all persons engaged in digging marl equally interested 

 in the preservation of bones which come under their notice, we might have 

 been far nearer an elucidation of this, one of the most extraordinary faunaj 

 which have been placed upon our planet. 



August 2&th. 

 The President, Da. Hays, in the Chair. 



Fourteen members present. 



Gen. S. Wylie Crawford, M. D., U. S. A. was elected a Member. 

 The following paper was presented by permission, reported on favor- 

 ably by the Committee appointed, and ordered to be published : 



Notes on the VESPERTILIONID.E of Tropical America. 

 BY H. ALLEN, M. D. 



I. 



The study of the Vespertilionidae of Tropical America has never been un- 

 dertaken by any one having large collections at his command. With others, 

 I have hitherto refrained from entering a field where such facilities, and an 

 acquaintance with type specimens, appeared to be necessary aids to produce 



1866.] 



