DESCRIPTION OF THE FOSSIL REMAINS. 65 



Of the system of median fins there are two dorsals situated very far back, 

 the anterior edge of the root of the first being 9^ inches distant from the end 

 of the snout. The first dorsal is remarkably slender and of a somewhat semi- 

 oval outline. Its base measures y^g- of an inch, while its total length is 

 about 1 J inch. Its anterior margin is nearly straight, the posterior being 

 much more convex. The anterior edge of the root of the second dorsal is 

 eleven and a half inches distant from the end of the snout. It has a very 

 similar form to the first dorsal, but is larger, measuring seven-eighths of an 

 inch along its base, and two inches along its longest axis, while its greatest 

 breadth is three-fourths of an inch. 



The dorsal lobe of the caudal fin begins about half an inch behind the 

 second dorsal, and opposite the commencement of the ventral Ljbe, the two 

 lobes being very nearly equal, and the tapering caudal end of the body being 

 but very slightly inclined upwards. The fin rays of the ventral lobe are 

 stronger than those of the dorsal lobe, and the end of the fin, which attains a 

 width of 24 inches, is abruptly truncated, so as to be something between 

 triangular and round in its contour. No lateral line is distinguishable, and 

 there is a mere indication of what appear to be the rays of the anal or 

 ventral fin, opposite the first dorsal, which last indeed looks so exceedingly 

 like a ventral fin that I was incliried to regard it as such, until Mr. Dinkel's 

 valuable suggestions led me to look into the question more carefully. 



The second specimen figured (Plate IV.) under the name of Glyptolcemus, 

 displays only the ventral surface of the anterior moiety, seven inches in 

 length, of a fish, whose transverse diameter nowhere exceeds two inches. 

 At the end of the block, to the left in the figure, the transverse section 

 of the body has the form of a transversely-elongated semi-oval, flat ven- 

 trally and convex dorsally, its depth from above downwards being about 

 an inch. 



The symphysial end of the lower jaw is rounded, the rami measuring 

 about two and a quarter inches in length. Their thickness is fully one- 

 fourth of an inch, and posteriorly they are an inch and a half apart. The 

 bony substance of the jaw is very thin, and where its- outer surface is pre- 

 served, it exhibits a ridged sculpture. 



The middle of the interval between the rami is filled by two large jugular 

 plates, which are separated from the rami by, apparently, five small plates on 

 each side. 



The large jugular plates have an elongated triangular form, and are two 

 and a quarter inches long, half an inch broad at ihe broadest ; the left being 

 rather wider than the right, and overlapping the latter by its uneven inner 

 edge. The bones are thin, and their posterior margins are rounded ; that of 

 the right side being broken. 



The surface of the plates exhibits a pitted and lineated sculpture, which is 

 so disposed as to radiate from a point near the outer margin of each plate ; 

 and, at about the junction of its anterior two-fifths with its posterior three- 

 fifths, the sculpture of the posterior part of the anterior division of each plate 

 is particularly coarsely reticulated. 



The small lateral jugular bones increase in length and in width from before 

 backwards, and exhibit a pitted or reticulated sculpture, which is coarsest iu 



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