ME. T. ATTHEY OiST PTEEOPLAX COElS'TrTA. 185 



Loxomma and Anthracosaurus, and the invariable absence of the 

 snout, maxillaries, and mandibles are the chief characteristics of 

 Pteroplax cornuta. The inferior parts of the skull being also 

 wanting in both our instances, renders it probable that Pteroplax 

 had a skull much less completely ossified than either of the two 

 animals above-named, and that it partook more than they did of 

 a batrachian or piscine character. 



That it had two pairs of limbs, feet or paddles, is very proba- 

 ble, and that it was an air-breather is evidenced by the form, 

 length, and breadth of the ribs, and perhaps also by the grooved 

 state of the under surface of the frontal bones. 



Of its body we know nothing beyond the scanty vertebrae, 

 fragments of ribs, and scutes. 



If, with the desire to form something approaching to a definite 

 idea of the comparative size of our three Labyrinthodonts, we 

 suppose the length of the animal to be seven times that of the 

 skull, which is about the proportion in Keraterpeton Galvani (a 

 comparatively short species), and if we allow two inches for the 

 lost part of the larger specimen of Pteroplax, the skull of this 

 animal, from the end of the snout to the end of the occiput, will 

 be seven inches and a half long, and the whole length of the 

 body four feet eight inches. 



By the same rule of the body being seven times the length of 

 the head we find that Loxomma AUmanni, with a skull twelve 

 inches and a half long, must have measured seven feet seven 

 inches ; and in like manner Anthracosaurus Russelli, with a skull 

 of thirteen inches and a half, must have had a total length of 

 eight feet two inches. The correctness, however, of this rule is 

 questionable ; and it is not easy to say what was the length of 

 the tail in each case. 



As was noticed in the '' Annals and Magazine of Natural His- 

 tory" for August, 1876, the jn-ajmaxilla figured in a previous 

 number as that of Pteroplax, and the teeth, as since shown by 

 an examination of their minute structure under the microscope, 

 as well as four or five fragments of mandibular bones, which had 

 been described as "most probably belonging to the same large 

 Labyrinthodont amphibian," all belong to Loxomma Allmanni ; 



