OF THE COUNTIES OF NORTHUMBERLAND AND DURHAM. 235 
greatest width is near the middle of the back. The scales are of 
a moderate size, much larger in the middle than on the upper 
and lower portion of the body. All the scales are covered with 
fine, wrinkled striz, which are disposed obliquely over the surface. 
3. P. parvus, Ag. 
Platysomus parvus, Ag., Poiss. Foss. ii., p. 170, pl. 18, f. 3. 
Chetodon, Winch, Geol. Tr. Ist ser., iv., pl. 2. ; Clanny, 
Ann. Phil. vi., p. 115. 
In Magnesian-limestone; very rare. Pallion, near Sunderland. 
The unique specimen, from which the following characters 
are taken, is at present preserved in the Sunderland Museum. 
It is exceedingly interesting, as well for its fine state of preser- 
vation as for being the first fish noticed in the Magnesian- 
limestone. It was first made known to geologists by Mr. N. J. 
Winch, who published a reduced figure of it, in the Geological 
Transactions. The figure given by M. Agassiz is only a copy 
of this, and as he has named it parvus, a name quite inappli- 
cable to this fine species, it is probable that he supposed the 
figure to be of the natural size. It is also figured by Dr. Clanny 
in the Annals of Philosophy. 
The general form is sub-rhomboidal, broadest near the posterior 
extremity. The head is rather angulated, and about one-third 
the whole length of the body. The fins are arranged, as in the 
preceding species, from the middle of the dorsal and ventral 
margins to the tail. The pectorals are rather small, and finely 
rayed, and the joints of the rays are rather distant, and 
longer than wide. The rays of the dorsal and ventral are 
rather distant, and strong; and the joints are short, and 
of the same width. The tail is comparatively very small, 
and only a small portion of the body is continued into its 
upper lobe. The rays of this lobe are very fine, but in 
the lower they are much stronger and closely articulated. The 
scales are rather large, rhomboidal or square, and arranged in 
curved rows from the anterior of the body to the tail. The 
scales are largest in the middle, and gradually decrease in size 
towards the upper and lower portions of the body. They are 
covered, as in the former species, with obliquely-arranged, finely- 
VoL, I. Ii 
