274 Dr. R. H. Traqnair on the Structure 



materially from those recorded by Dr. Young. To detail 

 briefly those results is the object of the present commu- 

 nication. 



Cranium proper. — I am quite unable to find any trace of 

 the large median " supraoccipitaV with its "crest," which 

 Dr. Young has figured* and described as interpolated be- 

 tween the parietals, as in ordinary Teleostei. On the contrary, 

 there is no doubt that in Amphicentrum, as in Ganoid fishes 

 generally (Lepidosteus, Polypterus, Amia, Lejridotus, &c. &c.) 

 and in some Teleostei {Maerodon, Erythrinus), the parietals 

 (p. PI. IX. fig. 1) were in contact with each other along the 

 middle line. On comparing Dr. Young's restored figure with 

 the skull represented in fig. 1, PI. IX., it is pretty evident 

 that he has designated the upper part of the supraclavicular 

 element of the shoulder-girdle as " parietal," while the real 

 parietal is included in his " frontal ;" a broken line across the 

 posterior part of the latter shows, at the same time, that the 

 line of separation, between the two bones did not altogether 

 escape his notice. On the outer side of each parietal is a 

 large squamosal (sq) ; and in advance of it there is a more 

 elongated fron tal (/). The latter does not, however, take 

 any part in the formation of the orbital margin, being sepa- 

 rated from it by two other plates (p.f & a./), the posterior 

 and anterior frontals, which form respectively the posterior- 

 superior and anterior-superior margins of the orbit. The 

 region of the skull between the prefrontals and the pre- 

 maxillaries is in all the specimens very obscure, though there 

 is evidence in this situation of a pair of square-shaped plates 

 representing nasals ; but I have not been able to discover any 

 median ethmoid. IS or are the nasal apertures apparent, though 

 probably they occur between each nasal bone and the large 

 anterior suborbital (to be subsequently alluded to). ^ Regarding 

 the condition of the base and side walls of the cranium nothing 

 more can be made out, beyond the presence of a strong para- 

 sphenoidal bar, which in some specimens is evident enough. 



Jaws and palato-quadrate apparatus. — The prcemaxillce 

 (p.mx) are generally plain enough, and are, as Dr. Young- 

 has described them, a pair of remarkable, prominent, sharp- 

 edged edentulous bones, forming a beak-like projection at the 

 front of the snout. Posteriorly each prasmaxilla articulates 

 with the maxilla of its own side. 



As regards the maxilla. Dr. Young has described it as an 

 oblong tooth-bearing plate, which " bulges below into an 



* Op. cit. p. 304, woodcut, fig. 1. 



