48 CEREBRAL DEVELOPMENT 



real sutures, but formed merely a kind of surface-tatooing, re- 

 sorted to as if for purposes of ornament. The cranial buck- 

 ler of the Asierolepis exhibited, as I shall afterwards have oc- 

 casion to show, a similar peculiarity ; both had their pseudo- 

 sutures, resembling those false joints introduced by the archi- 

 tect into his rusticated basements, in order to impart the ne- 

 cessary aspect of regularity to what is technically termed the 

 coursing and banding of the fabric. We can, however, de- 

 termine, notwithstanding the induced obscurity, that the buck- 

 ler of the Osteolepis was divided transversely in the middle 

 into two main parts or segments, — an occipital part. A, and 

 a frontal part, C ; and that the occipital segment seems to in- 

 clude, with the super-occipital, the parietal plates, and the frontal 

 segment to comprise, with its own proper plates, not only the 

 nasal plate, but also the representative of the anterior part of 

 the vomer. All, however, is obscure. But in our uncer- 

 tainty regarding the homologies of the divisions of this der- 

 mal buckler, let us not forget the homology of the buckler it- 

 self, as a whole, with the upper surface of the true cranium 

 in the osseous fishes. Though frequently crushed and broken, 

 it exists, in all the finer specimens of my collection, as a 

 symmetrically arranged collocation of enamelled plates, as 

 firmly united into one, though they all indicate their distinct 

 centres of ossification, as the corresponding surface of the 

 cranium in the carp or cod. The lateral curves in the fron- 

 tal part, immediately opposite the lozenge-shaped plate in the 

 centre, show the position of the eyes, which were placed in 

 this genus, as in some of the carnivorous turtles, immediately 

 over the mouth, — an arrangement common to almost all the 

 ganoids of the Old Red Sandstone. The nearly semicircular 

 termination of the buckler formed the creature's snout ; and 

 in the Osteolepis, as in the Glyptolepis and the Diplopterus, 

 it was armed on the under side, like the vomer of so many 

 of the osseous fishes, with sharp teeth. Some of my speci- 



