162 Tue Orrawa Naturatist. [January 
plastral lobe from side to’ side considerably in front of and in a 
general way parallel to the transverse gular sulci. Four infra- 
marginal shields are present on each side. 
Baéna pulchra is about half the size of B. hatcheri, from 
which it differs mainly in the proportions of the lobes of the 
plastron, the shape of the entoplastral plate and the disposition of 
the intergular and gular shields. A number of minor differences 
are seen in comparing the figures of the plastron. That the Belly 
River species closely approaches the Laramie form is evident and 
in B. pulchra we probably have the ancestor of the closely 
allied B. hatchert and B. marsht, Hay. The presence of a divided 
1st neural plate in B. pulchra is interesting. Two other Belly 
River species, Zrionyx foveatus, Leidy, and 7. vagans, Cope, have 
also been shewn by the writer to possess a corresponding divided 
plate. A detailed description of the carapace of B. hatcheri has 
been promised by the author of that species and possibly a full 
series of supramarginals, such as &. pulchra is seen to possess, 
may also be found in the former species. It may be interesting to 
note in this connection that the living species Macroclemmys tem- 
minckt (Alligator turtle) of the basin of the Mississippi and Mis- 
souri rivers has an additior | series of about four supramarginals 
intercalated betweed the costal and marginal shields. 
Other species of Chelonia from the Belly River series in 
Canada are 7rionyx foveatus, Leidy, Trionyx vagans, Cope, Adocus 
lineolatus, Cope, Bastlemys variolosus (Cope), Baéna antiqua, 
Lambe, and Neurankylus eximtus, Lambe. Besides the above, 
three species from the same horizon, have been described from 
material collected by Dr. G. M. Dawson in 1874 (British North 
American Boundary Commission*) ; these are Plastomenus coales- 
cens, Cope, Plastomenus costatus, Cope. anl Compsemys ogmius, 
Cope. 
After Leidy’s description, with figures, of Zrionyvx foveatus 
was published in 18609, little was added to our knowledge of the 
shell of this species until 1902 when the writer’s description of his 
*«* Report on the Vertebrate fossils from the Fort Union group of Milk 
River,” Appendix B by Prot. KF. D. Cope to ‘‘ Report on the geology and 
resources of the region in the vicinity of the forty-ninth parallel” by G. M. 
Dawson, 1875. 
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