ON BRITISH FOSSIL REPTILES. 181 



single ; in Naja it is almost divided into two, the upper being convex, the 

 lower moiety concave ; in the Python the upper half of the tubercle is con- 

 vex and the lower half concave, but the two facets are not marked oft". In the 

 Palccoplds, of both Sheppey and Kyson, it is simply convex. 



The most perfectly preserved, as well as the largest specimens of vertebrae 

 of Palceophis which I have seen, are from the Eocene clay at Bracklesham, 

 and are preserved in the select collection of Fr. Dixon, Esq. of Worthing. 

 The serpent to which the largest of these vertebrae belonged must have been 

 upwards of 20 feet in length. 



Ophidian reptiles, of ten, twelve, and twenty feet in length, exist in the 

 jiresent day only in intertropical regions, and they for the most part prey on 

 mammals and birds. If, therefore, direct evidence of species of both these 

 warm-blooded classes in the London clay had not been obtained*, they might 

 have been strongly suspected to have co-existed with serpents of such dimen- 

 sions as those to which the vertebrae and ribs above mentioned belonged. 



Order BATRACHIA. 



Of this order of Reptiles, represented in the present Fauna of Great 

 Britain by a few diminutive species of frogs, toads, and newts, the remains 

 of some remarkable extinct members have been discovered in the New Red 

 SandstQue of Warwickshire. 



As the determination of these fragments has been the result of the exami- 

 nation, in part microscopical, of detached bones and fragments of bone and 

 teeth, and since the Batrachian order, like most others at the confines of a 

 great natural group, exhibits wide modifications of its typical structure, a ievi 

 words may be expected touching the grounds for referring the fossils in 

 question to the Batrachian order, especially since similar fossils in another 

 country, specimens of the same species, have been regarded as parts of 

 Saurians. 



The Batrachians have no fixed type of external form like the higher orders 

 of Reptiles, but some, as the broad and flat-bodied toads and frogs, most 

 resemble the Chelonians, especially the soft-skinned mud-tortoises ( Trionyx) ; 

 other Batrachians, as the CcEcilia', resemble Ophidians ; a third group, as the 

 Newts and Salamanders, represent the Lacertians ; and among the Perenni- 

 branchiate reptiles there are species which combine with external gills the 

 mutilated condition of the apodal fishes. 



Thus it will be perceived, that, even if the entire skeleton of one of the 

 New Red Sandstone Batrachians had been obtained, there is no fixed or cha- 

 racteristic general outward ibrm in the Batrachian order whereby its affinity 

 to that group could have been determined. The common characters by which 

 the Batrachians, so diversified in other respects, are naturally associated into 

 one group or suborder of reptiles, besides being taken from the condition of 

 the circulating and generative systems and other perishable parts, are, how- 

 ever, fortunately as strongly manifested in modifications of th« skeleton and 

 principally in the skull. This is joined to the atlas by the medium of two tu- 

 bercles, developed exclusively from the lateral occipitals ; the bony palate is 

 formed chiefly by two broad and flat bones, called ' vomerine' by Cuvier, and 

 generally supj)orting teeth. It is only in the Batrachians among reptiles that 

 examples are found of two or more rows of teeth on the same bone, espe- 

 cially on the lower jaw (Cacilia;, Sireties). With regard to vertebral cha- 

 racters, no such absolute Batrachian modifications can be adduced as those 

 above cited from the anatomy of the cranium. Some Batrachians, as is well 

 known, have the vertebra; united by ball-and-socket joints, as in most recent 

 * Geological Transactions, second series, vol. vi. p. 203, pi. 21. 



