Acfiitopfioi'Hs (Jhtrki, Xeirherrii. — Claypole. 23 
oped in the branchiostegal membrane between the mandibular 
rami. 
These are an excellent preservation in the present specimen 
and form, as shown in the figure, a kind of fringe, composed 
of thin plates and covering the lower surface of the mouth, 
running backward from the lower margin of the mandible to 
meet on the median line a corresponding set from the oppo- 
site side. 
The individual plates are about two inches long and one- 
third of an inch in width and overlap slightl}^ at the edges. 
They are as thin as paper and apparently formed a pliable 
protection to the tissues beneath them. At the hinder end of 
the mandible these two sheets of chain armour parted on the 
medial line, leaving a space in which now lie the fragments of 
bone already mentioned, among which are probably the brok- 
en hyoids with some of the branchial arches in an unrecog- 
nizable condition. 
Many of the above details are rendered attainable by the 
fact that, although the fish lies, as did that of Ur. Newberry, 
belly upward, yet the head has been so pressed to one side 
during fossilization as to show that aspect in considerable 
perfection. This has prevented the crushing of the semi-car- 
tilaginous bones of the head into an indiscriminate mass as is 
usual with the fossil fishes from this shale. 
Not much can be added to Dr. Newberr3''s account of the 
pectoral fins. Tliey are well displayed in his specimen and 
only a few more details can be gathered from this one. The 
peculiar falcate form, the great number (OS in this case) and 
the remarkable thinness of the rays mark this species otf from 
all other known fossil fishes of the same horizon. Both the 
long and the short rays fork at about one-thirtl of their 
length from the base and again about as far from the tip so 
that their idtimate branches or trichinosts become excessively 
fine and give a very delicate texture to the edge of the fin 
which has no membranous border. 
The scapulo-coracoid arch is only seen as a broken and 
crushed nuiss, so that it is impossible to give any account of 
it. It may, however, be noted that the pectoral fins show dis- 
tinct signs of fulcra in the ailvance of the ganoid scales over 
the base of the ra3's in the hinder portion. 
