7 0 (Bulletin of the (Natural History Society . 
a is the rostral plate on which the little ridges are arranged 
parallel to each other, but transverse to the axis of the body. 
b, b, are the two anterior lateral plates on which the ridges 
are also parallel to each other throughout, and to the longer 
diameter of the plates, c is the dorsal scute, of which only a 
part is preserved, and in which the circular spot at the anterior 
end perhaps marks the position of the eye. On this plate the 
triangular area in front of this circular mark, extending for- 
ward to the rostral plate, is also marked by ridglets which are 
transverse to the axis of the body of the fish, but are not so 
regular, or so generally parallel to each other as those on the 
rostral plate. Behind the anterior triangular area on this 
plate, the little ridges extend backward, parallel in a general 
way to the axis of the body, to the posterior end of the plate: 
many of these ridglets are looped at the anterior end, where 
they are in contact with the triangular area of the plate above 
described; but going backward they become more distinctly 
parallel, and one can distinguish two sets, one of smaller and 
the other of larger ridges; there are about four or five of the 
more minute ridges between the larger ones; and the latter 
are not continuous, but result from a greater prominence 
being given to certain of the minute ridges for a limited dis- 
tance. This two-ranked arrangement does not characterize the 
ridges over the whole surface of the plate, but the margins on 
each side are marked, for a limited width, with parallel 
ridglets of uniform size, similar to those on the rostral and 
lateral plates. 
d is the ventral plate or scute on which the ridglets are 
similar in their size and arrangement to those on the dorsal 
scute. In the example found, one side of this plate is wanting. 
e, e , are portions of two lateral plates, which appear to have 
been posterior in position to the laterals b and b. f is a frag- 
ment of a plate on which the ridglets are curved; the position 
of this plate is doubtful. 
As this is the only Pteraspidian fish known which is 
