32 
Pt. Cumeri, 1 proceed to the description of the distinct species, for 
which I propose the name of Pterodactylus compressirostris. 
PTERODACTYLUS COMPRESSIROSTRIS, Owen. 
(Reptilia, Pl, V. figs. 1, 2 & 3.) 
This species is represented by two portions of the upper jaw, ob- 
tained from the Middle Chalk of Kent, the hinder and larger of which 
includes the beginning of the external nostril (figs. 1 & 2,7). The 
depth of the jaw at this part is fourteen lines, whence it gradually de- 
creases to a depth of ten lines at a distance of three inches in advance 
of this, indicating a jaw as long and slender as in the Pt. longirostris, 
supposing the same degree of convergence of the straight outlines of 
the upper and alveolar borders of the jaw to have been preserved to 
its anterior end: that this was actually the case is rendered most pro- 
bable by the proportions of the smaller anterior part of the jaw (figs. 
1', 2', 3'), obtained from the same pit, if not from the same block of 
chalk, and which, with a vertical depth of seven lines at its hinder 
part, decreases to one of six lines in an extent of one inch and a half 
in advance of that part. The sides of the jaw as they rise from the 
alveolar border incline a little outwards before they converge to meet 
at the upper border. This gives a very narrow ovoid section at the 
fore part of the larger fragment (fig. 2), the greatest diameter at its 
lower half being four lines, and the sides meeting above at a slightly 
obtuse ridge. This very gradually widens as the jaw recedes back- 
wards, where the entireness of the walls of the smoothly convex upper 
part of the jaw proves that the narrowness of that part is not due to 
accidental crushing. Had that been the case, the thin parietes arch- 
ing above from one side to the other would have been cracked. The 
only evidence of the compression to which the deep sides of the jaw 
have been subject is seen in the bending in of the wall above the 
alveoli, close to the upper ridge at the fore part of the fragment. 
In an extent of alveolar border of three and a half inches there are 
eleven sockets, the anterior one on the right side retaining the frac- 
tured base of a tooth: the alveoli are separated by intervals of about 
one and a half times their own diameter ; their outlets are elliptical, 
and indicate the compressed form of the teeth: they are about two 
lines in long diameter at the fore part of this fragment, but diminish 
as they are placed more backwards, the last two being developed be- 
neath the external nostril. The bony palate is extremely narrow, and 
presents in the larger portion (fig. 3) a median smooth convex rising 
between two longitudinal channels, which are bounded externally by 
the inner wall of the alveolar border. There is no trace of a median 
suture in the longitudinal convexity. The breadth of the palate at the 
back part of the fragment is eight lines; at the fore part it has gra- 
dually contracted to less than three lines, but it is somewhat crushed 
here. The naso-palatine aperture, p, commences about half a line in 
advance of the external nostril, three inches behind the fore part of 
the larger portion (fig. 3) of the upper jaw; which exemplifies the 
characteristic extent of the imperforate bony palate formed by the 
