58 



PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Apr. 20, 



of the sockets of the pair of upper canines in Oudenodon (PL I. 

 fig. 1 21), the surmise is suggested whether the species of this genus 

 may not originally have possessed tusks, which after being shed had 

 not been replaced, leaving the cavity of the sockets to absorption and 

 obliteration. Or it might be asked whether the Oudenodons may 

 not be the females of Dicynodons, in which, as in the Narwhal, 

 rudimental tusks may have been originally hidden in the substance 

 of the ridged tracts of the upper jaw, and afterwards absorbed. 

 Hitherto, however, I have not met with species of Dicynodon or 

 Ptycliognathus sufficiently resembling any Oudenodon in cranial 

 characters to support their ascription to the same species with merely 

 the sexual difference in respect to tusks. 



The following are admeasurements of some of the skulls of the 

 Dicynodont Reptiles above described : — 



Length of skull 



Breadth of occiput 



intertemporal space . 



interorbital space 



between the superorbital 



protuberances 

 skull anterior to the 



orbits 



across middle of alveoli 



of tusks 



internasal space . . 



each temporal fossa... 



Length of each temporal fossa 

 From hindmost part of skull to 



the orbit 



forepart of orbit to the fore- 



part of prernaxillary 

 Long diameter of orbit . . 

 nostril 



Greatest breadth of bony palate. 



Oudenodon 



Bainii. 



progna- 

 thus. 



in. lin. 



in. lin. 



6 5 

 5 6 

 1 2 

 11 



1 2 

 1 1 



1 6 



1 10 



2 8 



2 10 



9 



1 4 



2 6 



9 



3 10 





2 3 

 1 8 



11 



1 6 



2 8 

 1 9 

 8 



Greyi. 

 in. lin. 



10 



9 



1 3 



8 



2 4 



Ptychognathus 



declivis. 



in. lin. 



8 



6 4 



1 2 



2 8 



3 6 

 3 10 



2 8 



1 3 



2 6 

 2 3 



2 4 



3 9 

 2 2 



11 



1 5 



latiros- 

 tris. 



in. lin, 



8 6 



6 8 



1 7 



3 



4 

 3 6 



3 4 



1 7 



2 6 

 2 3 



2 7 



verti- 

 calis. 



in. lin. 



5 

 3 6 



11 



1 10 



2 6 

 2 8 



2 3 



10 



1 9 



1 9 



2 3 







Genus Galesattrus, Ow.* 



Ocdesaurus planiceps, Ow. (PI. II.) 



The shape of the skull on which the above genus and species are 

 founded is that of a narrow spade on playing-cards, the occipital 

 condyle forming the handle : it measures 3|- inches "in length and 

 2 inches 9 lines in extreme breadth across the zygomatic arches ; but 

 its greatest depth, including the lower jaw, does not exceed an inch; 

 and this diameter varies very little, the upper surface of the skull 

 being unusually flat and level. 



* From yaXtj, a weasel, and oaiipos, a lizard. 



