Section IV, 1918 [23] Trans. R.S.C. 



The Cretaceous genus Stegoceras typifying a new family referred 

 provisionally to the Stegosauria 



By Lawrence M. Lambe, F.R.S.C, Vertebrate Paleontologist 

 TO THE Geological Survey, Canada.^ 



(Read May Meeting, 1918.) 



The specimens on which the Belly River Cretaceous genus 

 Stegoceras was founded in 1902^ consist of the bones forming the 

 upper part of the brain-case. Since then other specimens pertaining 

 to this genus have been obtained, by vertebrate palseontological parties 

 of the Geological Survey, from the same formation in the same dis- 

 trict on Red Deer river. Alberta. The majority of these later 

 specimens consist of the same cranial elements as the type material, 

 but one includes elements not preserved with the foregoing, and the 

 remainder are cranial bones found separately and supplying addi- 

 tional or corroborative information regarding the structure of the 

 skull. The more comprehensive specimen, just mentioned, is in a 

 good state of preservation, is the best in every way so far collected, 

 adds considerably to our knowledge of the formation of the head in 

 Stegoceras, and is, for these reasons, made the subject of the following 

 description. It is probable that other parts of the skeleton of Stego- 

 ceras are included in the collections of different years from Red Deer 

 river but up to the present no bones except cranial ones have been 

 recognized as pertaining to the genus. 



The diapsidan nature of Stegoceras is revealed by the general 

 structure of the cranium in which two distinct temporal arches are 

 present. The laterotemporal fenestrae are large, the supratemporal 

 ones small or closed (secondarily reduced). 



Other primary characters divulged by the specimens available 

 are: — skull small, ending squarely behind, and overhanging in occi- 

 pital region, convexly elevated in parieto-frontal region. Superior 

 cranial elements, thickened by bone of a dense, vertical, columnar 

 structure; meeting in suturai facets of varying depth. Upper sur- 

 face, except central elevation, rugose with a wart-like sculpture. 

 Orbits large, placed well within the lateral borders. Head of quadrate 

 received in a cotylus in the squamosal. 



' Communicated with the permission of the Deputy Minister of Mines. 



^ Geological Survey of Canada, Contributions to Canadian Palaeontology, vol. 

 Ill (quarto), pt. II, On vertebrata of the Mid-Cretaceous of the North West Ter- 

 ritory, 1902. 



