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PROFESSOR H. G. SEELEY ON THE STRUCTURE, ORGANIZATION, 
the abdominal rods of Protorosaurus, and Mesoscairus, from South Africa ; but I shall, 
when dealing with the latter type be able to show that those rods are composite ribs 
comparable with the abdominal armature of Plesiosaurians. Professor Cope has also 
noticed abdominal rods in Stereosternum, and in a Batrachian genus Ichthyacanthus. 
No such structure is known in any Anomodont, but there is no evidence of its absence ; 
and a priori considerations suggest that it will be found. 
Professor Cope’s contributions to a knowledge of the skull are of great interest. 
The only genera which have been figured are Empedias and Naosaurus. The former 
is referred to the Diadectidfe, defined as Pelycosauria with transverse molar teeth. 
A cast of the brain cavity in this type has also been figured. The author describes 
the brain case as extending between the orbits, and in that family it is said to be 
completely closed in front, after the manner of Ophidians. Sir R. Owen has described 
a Theriodont Nytliosaurus {Galesaurus) (‘S.A. Cat.,’ Plate XXXIV., fig. 2) in which a 
similar condition appears to exist; only there is no such enlargement of the cerebral 
epiphysis in the South African fossil, and the American fossil, although widening 
anterior to the epiphysis, expands in a much less marked manner. It may be remarked 
in passing that the vertical foramen for the fifth nerve, figured by Professor Cope in 
the cast of the brain case, is quite in harmony with the vertical foramen similarly 
placed in Anomodoiits. In another genus, Edaphosaiiriis, Professor Cope describes a 
distinct element as connecting the basi-occipital on each side with the quadrate. This 
is not figured, but the description is suggestively indicative of the bone figured by 
Sir R. Owen in 1845 in Dicynodon lacerticeps, which was then regarded as the par- 
occipital. This bone is found to be characteristic of the Dlcynodontia. Professor Cope 
regards the skull in the Diadectidse as possibly forming the type of a sub-order, for 
which the name Cotylosauria was suggested. There is a plain facet on each side of 
the foramen magnum, which expands largely below these facets. The bone which 
bounds the forainen interiorly presents a vertical median posteriorly projecting process, 
on each side of which there is a transverse cotylus, much like those of an atlas wdiich 
are applied to the occipital condyles of the Mammalian skull. These concavities are 
further said to occupy precisely the position of the Mammalian condyles. The bone 
in which they are excavated is said to ha^’e the form of the Mammalian basi-occipital 
and of the Reptilian sphenoid. The author afterwards expressed doubt as to whether 
this form of articulation might not be due to the loss of a loosely articulated basi- 
occipital bone. This is the most distinctive feature of the Pelycosauria, but it does 
not appear to extend beyond the family Diadectidse. The occipital condyle is 
described as undivided in Edaphosaurus^ and, therefore, the argument tends towards 
the conclusion that the Cotylosauria may be distinguished from the Dicynodontia, but 
not to sustain the Pelycosauria without further evidence. The nearest approximation 
to this condition of the occipital articulation with which I am acquainted is that seen 
in the Placodontia ; and, in so far as I can judge from the evidences given in the 
figures of the skull of Empedias (‘Amer. Phil. Soc. Proc,’ vol. 19, Plate Y.), there are 
