4 BRITISH FOSSILS. 



Essay, I briefly adverted to the addition made to our knowledge 

 of the genus by the specimen received from Dr. Taylor of Elgin, 

 which I now proceed to describe at length. 



Glyptopomus minor. (PI. I., fig. 1.) 



This is a cast, in tolerably fine-grained sandstone, of an entire 

 specimen of Glyptopomus, the parts of which have undergone very 

 little derangement. The sandstone block in which the fish has 

 been preserved is split into two slabs, along a plane traversing 

 the body of the fish, and, in general, midway between its dorsal 

 and ventral surfaces. The one slab (fig. 1, PL I.) there- 

 fore, contains, for the most part, the impression of the dorsal 

 surface of the fish, while the other exhibits the impression of 

 its ventral surface; but the plane of splitting has not traversed 

 the head, so that the impression of the jugular plates and lower 

 jaw is left on both slabs. On the one, or dorsal slab, however, 

 it is the impress of the inner surface of the bone of these parts 

 which is shown, while, on the other, the outer or sculptured surface 

 has left its mark. 



The total length of the body of this fish is 13| inches ;\ it 

 attains its greatest width (2f inches) in the middle of its length. 

 Some allowance must be made, however, for the compression/to 

 which the fish has been subjected. / 



The greatest length of the head, measured in the middle/line, 

 from the anterior end of the snout to the level of the posterior 

 margins of the opercular apparatus, is 2f inches, or about one-fifth 

 the length of the body. 



The principal jugular plates (G) are each 2 inches long by 

 about three-quarters of an inch wide at widest. The impression 

 of their surfaces shows that they had had a finely-ridged, more or 

 less granular, sculpture. There is no median jugular plate, and 

 there is no positive evidence of the existence of any lateral jugular 

 plates. 



Behind, and partially overlapped by, the two principal jugular 

 plates there is evidence of two triangular sculptured plates be- 

 longing to the pectoral arch ; and behind these commence the 

 series of ventral scales, which are irregularly four-sided, about 

 a quarter of an inch wide by one-sixth of an inch long, and are 

 disposed in transverse rows, which converge obliquely from above 

 and without, downwards and inwards, to the middle line. The 

 surface of the cast of each scale exhibits a multitude of minute 

 hemispherical elevations, corresponding with the pits which 

 constitute the well-known ornamentation of the scales of this 

 genus. 



The median dorsal scales are irregularly hexagonal, and the 

 rows of lateral dorsal scales run from them as a centre, downwards 

 and backwards, on each side, to pass into the lateral ventral series. 

 The most anterior and largest of these median scales are as much 

 as four-tenths of an inch wide by a quarter of an inch in length. 



