292 PEOCEEDINGS OF THE GEOIOGICAI, SOCIETY. [May 7, 



under aspects of the head, and with the indubitable scales of this 

 remarkable fish ; and, putting the information thus obtained with 

 that derived from the study of specimens in many other collections, 

 I am now in a position to prove that Bhizodus is one of the cycliferous 

 Glyptodipterini. 



But, while looking through the large series of remains from the 

 Gilmerton ironstone in the Edinburgh Museum, most of which are 

 referable to EMzodus, I came upon two or three specimens of a very 

 different character. The most important and significant of these is 

 the fragment of the hinder part of the upper wall of a large cranium 

 (PI. XI. fig. 1) presenting its smooth inner, or under, surface to the 

 eye. Where the substance of the bone has been broken away, however, 

 the impressed surface of the matrix shows that the outer, or upper, 

 surface was ornamented with strong inosculating ridges separated 

 by intermediate grooves. The serrated sutures of the bones com- 

 posing this fragment of a skull are, for the most part, distinctly 

 traceable, and prove it to be composed of two quadrate, supraoccipital 

 elements, with two elongated parietal bones, the apposed edges of 

 which are deeply notched at the junction of their middle with their 

 posterior third, so as to give rise to a rounded parietal foramen, 

 •j^ths of an inch wide. The parietals unite, in front, with a pair 

 of frontals, which are narrow behind, but expand anteriorly, and 

 then become broken and disfigured. An arcuated postfrontal is 

 connected with the posterior moiety of the outer edge of each frontal, 

 and with the antero-external edge of the parietal. Externally, its 

 smooth, almost vertically bevelled, margin bounds the inner and 

 posterior part of the orbit. The latter cavity has an irregularly oval 

 shape, the long axis of the oval being directed, from without and in 

 front, obliquely inwards and backwards, at an , angle of about 45° 

 with the long axis of the skull. The anterior and outer part of the 

 waU of the orbit is broken away ; but, internally, it is bounded by a 

 stout prefrontal, on the under face of which is the indication of a 

 ridge, now broken away, but which once projected towards the palate. 

 The prefrontal joins the postfrontal and, just in front of the junc- 

 tion, expands, somewhat suddenly, outwards, so as to form a sort of 

 promontory which disturbs the even contour of the orbit on its inner 

 side. 



The postero-lateral boundary of the orbit is formed, in its hinder 

 half, by a postorbital bone, and, in its anterior half, by what appears 

 to be the jugal bone. All that remains of the outer boundary is a 

 trihedral bar of bone 0*5 inch wide, which I take to be the hinder 

 part of the maxilla, though it may be the continuation, forwards, of 

 the jugal. This bony bar is concave on its outer or upper surface, 

 which is coarsely sculptured, while its inner and outer surfaces slope 

 towards one another, so as to form an edge below, which is sharp in 

 front and gradually dies away behind. The outer face is flat, and 

 exhibits a delicate rugose sculpture : the inner is slightly excavated. 



Behind the orbit the lateral part of the roof of the cranium widens, 

 and is produced, at its external and posterior angle, into a broad, 

 expanded, and irregularly shaped plate, whose extreme outer point 



