CROCODILIANS, LIZARDS, AND SNAKES. 181 



This common ancestor is a land rejitile with the peculiar character 

 of the paroccipital seen in the Pythouomori)ha. Wliether it would 

 enter this suborder remains to be ascertained. From it the Saurian 

 type has been derived by the reduction of the paroccipital, and its wide 

 remova? from the cranial wall. The ophidian order has resulted from 

 an enlargement of this element, together with its exclusion from the 

 cranial walls, to which it nevertheless remains adherent. Boulenger' 

 suggests that the IJoIichosauria occupy this position. 



The Squamata display among Reptilia tendencies Avhich reach their 

 extreme expression in the Ophidia. These are, as already pointed out, 

 first, the disposition to reduction in the use of the limbs as supports of 

 the body, and a consequent increasing tendency to rest the body on the 

 ground when in motion; second, the increasing mobility of the suspeu- 

 sorium of the mandible, permitting an increase in the gape of the 

 mouth, and the consequent capacity for swallowing large bodies. 

 These tendencies are seen, first, in the successive shortening of the 

 limbs and reduction in the number of the digits, and finally reduction 

 and abolition of the limbs themselves. It is characteristic of the entire 

 suborder that the ribs have only the tubercular articulation with the 

 veterbra', having lost the capitular, thus reducing the strength of the 

 suspension of the viscera from the vertebral column. It thus becomes 

 first comfortable, and finally necessary that the body should be sup- 

 ported by the earth or object on which the animal rests, the process 

 being identical with that which has taken place in the Cetacea, which 

 have also lost the capitular rib articulations after long suspension of 

 the body in the water. This change is, of course, completed by the 

 total loss of limbs, as is seen in many Sauria and in all Ophidia. The 

 freedom of the distal extremity of the quadrate bone gives mobility 

 to the mandible; but this function does not reach any great develop- 

 ment in the Sauria, and is but little more obvious in the inferior 

 Ophidia (Angiostomata). In the Ophidia generally it acquires an 

 enormous development, most of all in the highest venomous forms 

 (Solenoglypha). 



5. HISTORY. 



The order Scjuamata was first correctly delimited by Merrem in 1820,^ 

 who included in it only the Sauria and Ophidia. The name was pro- 

 posed by OppeP in 1811, but he included in it the crocodiles. The 

 character viewed by these authors as definitive was the possession of 

 tegumentary scales, in contrast to the osseous carapace of the Testudi- 

 nata. They were unacquainted with the various anatomical characters 

 which distinguish the order from all others. The Sauria and Ophidia 

 were regarded as orders by other authors, including Dumeril, in accord- 

 ance with the system of Brcmgniart (1799). 



The first author to define the Squamata by anatomical characters 



' Proceedings, Zoological Society of London, 1891, p. 118. 

 '^ Versuch eiues Systems der Aniphibieu, Marburg. 

 ''Ordnungen Familien u. Gattungen der Rejitilien, Miinchen. 



