R. Lydekker—Note on the Ichythopterygia. d13 
identical with this form, but since, as I shall show on a subsequent 
oceasion, that species appears to have been founded by mixing up 
the characters of two specimens, which are apparently specifically 
distinct, the name must be abolished. 
It is not improbable that one or more of the Kimeridgian species 
mentioned in the Campylodont subgroup may be referable to Ophthal- 
mosaurus, and I think there is considerable probability of this being 
the case with Ichthyosaurus (?) ovalis, in which the contour of the 
vertebre differs considerably from that obtaining in Kimeridgian 
species undoubtedly belonging to Ichthyosaurus. It may therefore 
prove that Ophthalmosaurus icenicus is even specifically identical with 
this form. In respect of other species, I have great doubt whether I. 
enthectodon is distinct from the continental I. leptospondylus of the 
same geological horizon, but since I cannot certainly say that the two 
are identical, it is preferable to allow both names to stand for the 
present. I find by a comparison of the type skulls of the so-called 
I. Zetlandicus! of the Upper Lias of Whitby, and J. longifrons of that 
of Normandy, that these two are evidently closely allied forms ; and 
since certain differences in the arrangement of the bones of the 
quadratic region do not appear to me to be, at the most, of more than 
racial importance, I am inclined to refer both forms to a single 
species. A comparison of the pectoral limb of the Normandy torm 
with that of the Whitby I. acutirostris shows, moreover, that both 
are of the same structural type ; and since other Upper Liassic skulls 
from Whitby, which are indistinguishable from the type of I. Zetland- 
icus, agree equally closely with that of the former, I am disposed to 
unite both I. Zetlandicus and I. longifrons with I. acutirostris. I find, 
moreover, that skeletons from the Upper Lias of Wiirtemberg in the 
Museum, which agree with the one figured by Renevier in the “ Bull. 
Soc. Vaudois ” for 1885 as I. quadriscissus, Quenstedt, and also with 
those from the same region figured by Prof. Seeley in the ‘ British 
Association Report ” for 1880, without specific determination, present 
all the characters of the present species. And J am confirmed in 
this conclusion by finding it stated by Theodori in his Monograph 
of I. trigonodon that I. acutirostris is the most common form found 
in the Upper Lias of Bavaria and Wiirtemberg. The sketch of a 
skull from the Upper Lias of Banz, in Bavaria, made by Theodori 
_and presented by him to Sir R. Owen, which is preserved in the 
British Museum, also affords important evidence in this direction, 
since it shows that the premaxilla and lachrymal did not unite below 
the nares to exclude the maxilla from that aperture ;—a feature which 
is characteristic of the skulls described as I. Zetlandicus and I. 
longifrons. 
I may observe also that, as Mr. W. Davies first pointed out to 
me, I. longirostris, Owen, appears to be identical with I. latifrons, 
Konig. The former name was, however, originally applied by Jager 
1 T am glad to take this opportunity of thanking Prof. T. McKenny Hughes, of 
Cambridge, for his courtesy in permitting the type skull of I. Zetlandicus to be sent 
to the British Museum for comparison. 
