ON DORYPTERUS HOFFMANNI. 257 



largest of the hour-glass-shaped plates are three-sixteenths of an 

 inch in length. These, in their arrangement and situation, re- 

 semble fin-supports. 



A similar series of hour-glass-shaped plates extends along the 

 ventral margin immediately within the base of the anal fin, and 

 are large in front for some short distance backwards, corres- 

 ponding to the space occupied by the enlarged anterior portion 

 of the fin. These large plates and the large ones at the root of 

 the dorsal seem to be articulated with the fin-rays. 



The whole of the transverse plates, areas, and rods, as well 

 as the ventral plates and columns and great posterior abdominal 

 rods, seem as if covered with black enamel-like matter, having a 

 semigloss similar in appearance to that which covers the head- 

 bones and fin-rays. Indeed some of them seem as if composed 

 of nothing else ; and such is the appearance of a few of the cra- 

 nial bones themselves. The bony support, however, can be 

 traced in some of them ; and a few of the lateral rods are hollow, 

 the bony or cartilaginous support having apparently disappeared. 

 But this enamel-like matter does not seem to have been confined 

 to these parts ; it appears to have been continued as a thin film 

 composed of granules between the series of plates, and was ex- 

 tended over the entire surface of the fish as a dermal envelope, 

 the plates and rods being, as it were, immersed in it. Such is 

 the appearance particularly in the region of the sigmoidal ridges, 

 where there is a continuous darkish film of considerable thick- 

 ness, having a granulated surface, and giving the appearance to 

 them of a series of broad continuous plates, which in all proba- 

 bility they are, the grooves in the ridges limiting the anterior 

 and posterior margins of each plate. And there is usually, ex- 

 tending from the margin of the lateral plates, a broken fringe 

 (figs. 2, 3, v) of black matter continuous with that which covers 

 the plates, and which seems to be the remains of the ruptured 

 film or dermal envelope. In fact, in one or two places where 

 the plates are more approximated than usual, the continuity of 

 the connecting film is quite obvious. 



Now comes the question, Are the whole of these plates and 



R 



