176 



THE EXTINCT BATRACIIIA, REPTILIA 



with unsatisfactory results. While Faujas believed it to he a crocodile, ( lamper and ( 'uvier 

 regarded it as a, lacertian, and placed it near the Monitor. In the latter relation it has 

 been allowed to remain by Goldfuss and Owen, who have since written upon it, and so it 

 continues to he regarded by all palaeontologists of the present day, who have expressed an 

 opinion on the subject. 



I have, however, been able to demonstrate, by the light of new material recently dis- 

 covered, that the Mosasaurida.e ami Clidastidae constitute; a peculiar order of Reptiles, 

 which possesses a combination of the characters of Serpents, with those of Lacertilia, and 

 some others of the Sauropterygia. The reason why, as I conceive, this genus and its allies 

 have been so little understood, lias been a lack of analysis of the structure of portions of 

 the cranium little known, as well as of portions better known, and the lack of certainty 

 as to the structure of the limbs. 



The characters of the order arc as follows : 



First. The teeth have no fan^s. 



Second. The opisthotic bone projects free from the cranium, and is the snspensoriuin 

 of the os quadratum. 



Third. Then 1 is no columella. 



Fourth. There is no symphysis mandibuli. 



Fifth. The parietal is decurved posteriorly, and extends to the (sphenoid, forming the 

 cranial wall in front of the prootic. 



Sixth. The subartieula.r and splenial elements of the mandible are connected by artic- 

 ular faces. 



Seventh. The vertebrae arc very numerous, much exceeding one hundred, and frequently 

 present the zygosphen articulation. 



Eighth. The abdominal cavity is long and is surrounded by many short curved ribs, 

 which have simple heads and a free antero-posterior movement on vertical articulating 

 surfaces, and which commence close behind the axis vertebra. 



Ninth. The pterygoids are elongate and bear numerous teeth, and in one type are free 

 except at the; extremities. 



Tenth. The brain case is not fully ossified anteriorly. 



Eleventh. Scapular and coracoid elements are present. 



Twelfth. The caudal vertebrae are furnished with chevron hones. 



Thirteenth. The squamosal bone is present. 



Fourteenth. The angular bone is distinct. 



Fifteenth. The os quadratum is moveably articulated to the opisthotic. 



Sixteenth. The os quadratum embraces and encloses the meatus auditorius externus. 



Seventeenth. The opisthotic is supported by a, pedestal projecting from the cranial 



