44 



NEW YORK STATE MUSEUIV 



The following detailed account of the structure of this extremely 

 important species has been compiled chiefly from the recent papers of 

 Traquair and Patten, cited in the above references to the literature. 



The head shield occupies nearly one third of the entire length of the 

 armoring, and shows, on the upper surface, an orbital opening which is 

 smaller and further back than in Asterolepis. The median occipital plate 

 [text fig. lo m. occ^ has its lateral margin more perpendicular to the pos- 



Fig. II Restoration of ventral surface of same, slightly modified (After Traquair) 



terior one than in the last named genus ; its anterior aspect shows not 

 merely a shallow reentering angle for the postmedian plate, but a deep 

 semielliptical notch or excavation, on each side of which it takes part in the 

 formation of the posterior boundary of the orbit. Consequently the post- 

 median plate is small, entirely received in the aforesaid notch of the 

 median occipital, and thus excluded from joining the laterals as in Pterich- 

 thys and Asterolepis. The lateral occipitals [/. occ^ and the angular Sjxg\ 

 do not call for any special comment, but the laterals [/] are much broader 

 than in Asterolepis, while the extralaterals \c. /.] are verv small, narrow, and 

 pointed in front. 



