24J.. REPoiiT — 1873. 



dence brought to light since the date of Professor Owen's memoir. We still 

 know very little about the limbs of Triassic Labyrinthodonts. What is known 

 of the limbs of the Carboniferous species does not at all agree with the deter- 

 minations in question. But it is now placed beyond dispute that in Triassic 

 rocks, and in this very Keuper quarry at Warwick, the remains of Dinosauria 

 occur. The ilium assigned to Lahyriniliodon pacliygnathus * agrees with the 

 ilium of Dei7iosauria in the remarkable projection of the bone in front of the 

 acetabulum, and in the character of the acetabulum itself. It wants, it is 

 true, the pre- and postacetabular processes of a TveU-characterized Dino- 

 saurian ilium ; but in*no particular does this bone agree with the ilium of 

 any known Labyrinthodont. There is nothing in the structure of any one of 

 the limb-bones or vertebrae attributed to L. pachygnatlius which does not 

 accord at least as well with the Dinosauria as with the Labyrinthodonts f. 

 Nor is there a single distinctive Labyrinthodont feature about Cheirotherium. 

 Some of the footprints included in this heterogeneous group may have been 

 Labyrinthodont ; but others are, not improbably, Dinosaurian J. Shortness 

 or deficiency of the outer digits §, and inequality of fore and hind limb, are 

 characteristic of this reptilian order |!, 



It may be said, summarily, that the Labyrinthodonts of the Coal-measures 

 had the limbs of aquatic animals similar to the urodele Amphibia, and that 

 the limbs of the Triassic species are practically unknown. 



No limbs have been discovered belonging to specimens of Ophklerpeton, 

 although several examples belonging to this genus have occurred in the coal- 

 fields of Kilkenny and Northumberland. 



Hyoid. — We have no certain knowledge of the hyoid of any Labyrinthodont. 

 A fragment of a styloid bone which sometimes appears between the para- 

 sphenoid and the median thoracic plate of Archegosaurus, associated with one 

 or two pairs of lateral appendages, may belong here. 



Branchial Arches. — Goldfuss ^ first observed that some young examples of 

 Archegosaurus exhibit distinct traces of branchial arches ; and this determi- 

 nation is confirmed by Von Meyer. The evidence consists of minute ossicles 

 lying scattered in the region of the throat, between the thoracic plates and 

 the skull. Some of the ossicles exhibit a pectinate edge. They are variously 

 discoidal, semilunar, or quadrangular in outline, but always flattened. Von 

 Meyer believes that the branchial arches were attached to the hyoid, and 

 were disposed in two or more curved rows. Traces of branchial arches have 

 only been detected in young specimens ; and they do not increase in size with 



* '■ The remarkable ilium ascribed to Lahyritithodcm pachi/gnatJms is also a reptilian 

 bone, intermediate in its characters between the ilium of a Teleosaurian and that of a 

 Lizard." — Huxley, ' Geol. Journ.' vol. xxri. p. 47 (1870). 



t The fragmentary vertebra ascribed by Prof. Owen to L. pacht/gnathus is believed by 

 Prof. Huxley to be Dinosaurian (Quart. Joiirn. Q-col. Soc. 1870, vol. xxvi. p. 47). 



\ The Clieirothorian footprint figured and described by Prof. W. C. Williamson (Quart. 

 Journ. Geol. Soc. vol. xxiii. p. 56) exhibits numerous impressions of scales. This is a 

 re]5tilian feature, though not conclusive against the Labyrinthodont supposition. 



§ Iguanodon has left large three-toedimpressions in the Wealden. Scelidosaurus had 

 four toes and a ruduuentary fifth, 



II " From the great diflerence in size between the fore and hind limbs, Mautell, and more 

 recently Leidy, have concluded that tlie Dinosauria (at least Iguanodon and Hadrosaiirus) 

 may have sujiported themselves for a longer or shorter period upon their hind legs. But 

 the discovery made in the Weald by Mr. Beckles, of traces of large three-toed footprints, of 

 such a size and at such a distance apart that it is difficult to believe that they can have 

 been made by any thing but an Iguanodon, lead to the supposition that this vast reptile, 

 and porha)3s others of its family, must have walked temporarily or permanently upon its 

 hind legs."— Huxley, 'Quart. Journ. Geol. Soc' vol. xxvi. p. 18 (1870). 



T[ Beitriige, p. 8. 



