578 Loxomma Allmanni in the Northumberland Goal-field. 



the parts, we were quite unable to determine to which of the 

 known forms to refer them, until the possession of the speci- 

 men under discussion cleared up the matter. We can now 

 trace distinctly the presence of the central portion of the cra- 

 nium, which agrees with that before us in form and surface- 

 sculpture. A portion of a maxilla, with a few teeth attached, 

 as well as considerable remains of the lateral expansions, are 

 likewise determinable. 



Having now the advantage afforded by the possession of 

 this almost perfect skull oi Loxomma Allmanni , we are also 

 enabled confidentl j to refer to the two magnificent Labyrintho- 

 dont skulls exhibited and described, under the name of Ptero- 

 ])lux hrevicornisj by Mr. James Thomson and Prof. Young, of 

 Glasgow, at the meeting of the British Association held last 

 year at Exeter. On passing through Newcastle on his road 

 homewards, Mr. Thomson kindly gave us an opportunity of 

 inspecting these specimens ; and at the time we pronounced 

 them to belong to Loxomma — certainly not to Pteroplax. We 

 are now in a position to speak on the subject without the 

 least hesitation, in confirmation of our opinion then expressed. 

 That our cranium is that of Loxomma^ there is not the least 

 doubt ; that it agrees with Mr. Thomson's specimens generi- 

 cally, and, we believe, specifically, is equally certain ; and that 

 Pteroplax is distinct from Loxomma^ we have the high autho- 

 rity of Prof. Huxley, who has examined our type specimens 

 of the former. 



This is quite evident even on a cursory examination of the 

 two forms. But we may take this opportunity to state that 

 Pteroplax deviates considerably, in the structure of the cranium, 

 from all known Labyrinthodonts. In the conformation of the 

 head it approaches the Siren. This fact was entirely over- 

 looked by us at the time of the pul)lication of our paper on the 

 subject (Ann. Nat. Hist. ser. 4. vol. i. p. 260), and was not 

 recognized until Prof. Huxley kindly pointed it out to us 

 some time afterwards. 



Pteroplax has no posterior lateral expansions like those in 

 Anthracosaurus and Loxomma^ as we thought it would have 

 (the whole, or nearly the whole, of the cranium is figured in 

 plate XV. fig. 1 of the above paper) ; the maxillaj are also 

 deficient. The long curved horns are undoubtedly the equi- 

 valents of the lateral external cornua in Loxomma ; and the 

 overlying points are the homologucs of the inner horns, being 

 in both genera the posterior extremities of epiotic bones. 



Shortly before the occurrence of the cranium of Loxomma 

 at Newsham, Mr. Atthey obtained from the same locality a 

 series of vertebrae, lying nearly in natural order, with a few 



