262 MESSES. HANCOCK AND HOWSE 



head, in particular, has greatly suffered, the upper margin being 

 entirely obscured by the opercula (s), which have been torn 

 from their natural positions and turned upwards and forwards ; 

 their lower extremities are placed close together, and project in 

 front of the brow. They lie with the external surface upper- 

 most, their anterior margins approximating. That belonging to 

 the right side has carried along with it the pectoral fin (c), which 

 is beautifully displayed, in an expanded state, almost complete. 

 The left pectoral is distinctly seen in its natural position, though 

 much injured, and overlain by a thin film of apparently the skin. 

 The mandibles are not disturbed, and by their position indicate 

 that the mouth was closed ; but the bones of the upper jaws are 

 not determinable, except the left maxilla, which is in a pretty 

 perfect state ; the prsemaxilla, however has been torn away. 

 The orbit (u) is pretty well preserved, but is removed a little 

 below the natural position. 



The contour of the dorsal margin, in front of the dorsal fin, is 

 entirely lost, this region having been forced downwards nearly 

 as far as the centre of the body. Posteriorly, however, the 

 whole form is well preserved, and exhibits the transverse plates 

 and rods in a good state of preservation, the series of lateral (g) 

 and sigmoidal plates (j) being almost complete ; the line of the 

 central lozenge -shaped plates (h) is also quite distinct, with a 

 plate here and there bearing a central ridge. In front this line 

 is thrown suddenly upwards, in consequence of the ruptured 

 condition of the anterior parts. Twenty-eight lateral plates can 

 be counted, and fifteen or sixteen sigmoidal ones along the lower 

 margin ; only ten or eleven can be made out of the dorsal row. 



One of the most interesting features in this specimen is the 

 ventral plates (m), which are displayed in a remarkable manner. 

 Without the aid of this specimen it might have been difficult to 

 determine the existence of a double series of these plates, one 

 belonging to each side of the abdomen. Here, however, both 

 sets are most satisfactorily seen, those belonging to the exposed, 

 or left side, being arranged in their natural order, while those of 

 the right side are turned downwards below the ventral margin, 

 so that their outer surface is placed upwards, and in the same 



