DESCRIPTION OF THE SPECIES OF PTERYGOTUS 253. 
squamz, but only near the upper end and about the notch. This 
post-oral plate is the broadest of any species known. 
Fig. 16 isa plate of the same nature as those found with P. dudenszs, 
and is possibly a thoracic or abdominal appendage, though, as no 
species are known with any such attached, its nature is quite doubt- 
ful. The small crenate fragment, fig. 17, probably belongs to it; a 
similar piece is attached atc to fig. 16. [The entire form is better 
seen in P. arcuatus, Plate XIII. [Plate 24] fig. 16, viz, a lobed 
broad emarginate plate (d), in the wide notch of which is attached 
the truncated sub-oval plate a, 4.) A more perfect specimen is here 
added in a woodcut, showing the thickness of the plate on the one 
side of it. The obscure converging lines ending in serrations on the 
border are exhibited on one surface; on the opposite, the oblique 
close plicz running into parallel lines towards the margin, very like 
the segments of a feather. 
The base a a@ is much extended on each side, and in this respect 
seems to be different from the figure above quoted, Plate XIII. 
[Plate 24], which probably belongs to P. arcuwatus. 
Localities —UPPER LUDLOW Rock, Whitcliffe, and many places 
near Ludlow (Ludlow Museum and Museum of Pract. Geology ; 
Cabinets of Messrs. Lightbody, Cocking, J. Harley, and A. Marston). 
Kendal, Westmoreland (Museum of Pract. Geology). Ludlow Bone 
Bed, Ludlow ; Downton Sandstone of Bradnor Hill, Kington. (Mr. 
R. Banks’ Cabinet.) BASE OF OLD RED SANDSTONE, Ludlow 
Railway Station (Museum of Pract. Geology). Cornstones of Hopton 
Gate (Cabinet of Mr. J. Harley). 
One of the most widely spread species ; it is probably this which 
occurs in the Upper Llandovery Rock or “ May Hill Sandstone” of 
the Obelisk, Eastnor Park. A woodcut of it is subjoined. 
FIG. 13. 
fragments of ectognaths. Eastnor Park, Malvern. 
(Cabinet of Sir W. Jardine.) 
Plerygotus problematicus, Agass. ? 
