ee 
1906] A NEw CHELONIAN GENUS FROM ALBERTA 2B2 
intergular shield divided ; inframarginal shields present on the 
bridges. 
The specific characters of Boremys pulchra, the type of the 
genus, are :— 
Costal shields short and pointed distally ; supramarginals 
well developed, longer than broad ; first neural plate divided ; 
entoplastral plate narrow, diamond shaped ; plastron longer than 
broad ; anterior plastral lobe smaller anc more pointed than the 
posterior lobe ; bridge long and rather narrow. 
In Laéna arenosa, Leidy, 1870, from the Bridger Eocene of 
Wyoming, the type of the genus, there are no supramarginals, 
ner are there any in B. undata, Leidy, 1871, also from the Bridger 
Eocene of Wyoming. In the latter species the mesoplastral plates 
(not shewn in Leidy’s figure of the plastron of the type specimen) 
converge toa point inwardly and meet in the median line. 
The following Eocene, Laramie and Cretaceous species have 
been assigned to the genus Baéna :— 
B. hebraica, Cope, 1872. Bridger Eocene of Wyoming ; no 
supramarginals. 
B. ponderosa, Cope, 1873. Bridger Eocene of Wyoming; 
known only from small fragments of carapace. 
B. hatchert, Hay, 1901. Laramie of Wyoming ; no mention 
of supramarginals in the carapace. 
B. marsht, Hay, 1904. Laramie of Wyoming ; no mention 
of supramarginals in description. 
B. cephalica, Hay, 1904. Laramie of Wyoming; known 
from the skull only. 
B. antiqua, Lambe, 1902. Belly River (Judith River) forma- 
tion of Alberta ; type specimen does not include the distal ends of 
the costal shields. 
Relying on the presence of supramarginals as the chief char- 
acter of the carapace of Boremys by which this genus Is to be dis- 
tinguished from Baéna it is clear that information regarding the 
structure of the carapace in some of the species of the above list 
is needful before their true generic affinities can be fully deter- 
mined. Judging from the shape of the mesoplastral element (in 
combination with a divided gular shield and the development of 
