70 Miscellaneous. 



Euchyrosaurus the centra are composed of a median part, or hypo- 

 centrum, and two pleurocentra not soldered together, in Stereorachis 

 the centra are in a single piece, which adheres to the neural arch ; 

 the vertebral column has therefore acquired much more solidity, 

 which has led me to invent the name Stereorachis. It must, how- 

 ever, be noted that the centra of the vertebrae were stiU extremely 

 hollow ; their anterior and posterior faces were so concave that they 

 formed two cones united end to end ; I would not even assert that 

 there was not a perforation establishing the continuity of the 

 notochord. This is a condition analogous to that of many 

 fishes. 



The new genus found by M. Roche presented another mark of 

 superiority over the Reptiles that lived with it. Its humerus had a 

 neuro-arterial canal in its distal part. I had already called atten- 

 tion, in Euchyrosaurus, to the rudiments of the arch indicating a 

 tendency to the formation of this canal ; in Stereorachis the forma- 

 tion was completed. When we find that, besides the neuro-arterial 

 canal, the humerus had its epitrochlea and its epicondyle widened 

 as in those animals in which the supinator and pronator muscles, 

 or the extensor and flexor muscles, are greatly developed, we are led 

 to think that the old quadruped of Igornay had arms more perfec- 

 tionated than those of existing reptiles. 



Stereorachis must have been a carnivorous animal of considerable 

 size ; one of its mandibles, although a little broken, measures 18 

 centims. The upper and lower jaws are armed with conical teeth, 

 deeply immersed in the sockets ; their section is nearly circular ; 

 they are smooth externally, with a radiate structure in the interior ; 

 the front ones are stronger than the rest ; an inferior tooth has a 

 crown 32 millims. high ; a superior tooth, the point of which un- 

 fortunately is broken, must have been at least 40 millims. There 

 is an entosternum which recalls that of the Labyrinthodonts ; it is 

 very broad in its anterior third, and narrowed behind ; its length 

 is 15 centims. Eeside it there is a large nearly quadrilateral bony 

 plate, 14 centims. long and 5 centims. broad ; I suppose this to be 

 the homologue of the coracoid and scapula. There is also a curved 

 bone which I believe to be the homologue of the great bone in fishes 

 regarded by Mr. Kitchen Parker as a clavicle (episternum of the 

 Ganocephalous reptiles). I must also notice long arched ribs, 

 formed of two pieces united end to end ; a large coprolite ; bones of 

 the head with a rugose surface ; and hard, brilliant, very fine, long, 

 aciculate scales, as in Archeyosaurus and Actinodon. 



In some respects Stereorachis shows affinities with the Gano- 

 cephala and Labyrinthodonts. In other respects it shows tenden- 

 cies towards certain genera of the Permian of Russia and the Trias 

 of South Africa, upon which Prof. Richard Owen has made admi- 

 rable investigations, and for which he has proposed the name of 

 Theriodonts. Perhaps it still more nearly approaches some North- 

 American animals, such as Empedocles, Clepsydrops, and Dimetro- 

 don, ranged bj Prof. Cope in his group of Pelycosauria ; but at 



