f 
1878.] Geology and Paleontology. 565 
- taken place in the course of development of the ETSE SSRS order. 
These changes consist in the advance forwards of the external 
nares, the more posterior location of the hens tates tie 3 in- 
teeth, and the change from amphiccelous to proccelous vertebral 
articulations. 
Prof. Owen proposes that these changes were concomitants of 
a gradual restriction of aquatic and increase of terrestrial habits, 
and the gradual diminution of a purely fish diet, and the adoption 
of land animals as food. The capture of the latter and their 
retention below the surface of the water until devoured, directly 
relate to the uses of, and hence necessity for, the new structures 
in question, 
A new Diapecres.—This very singular pan of supposed 
Saurians, is represented by a third species from the Permian of 
Texas. The teeth are more completely molar in tiei character 
than in the species already described, being in the unworn condi- 
tion as broad across the crown, as the latter is high. In the 
transverse direction the crowns are two and half times as long as 
wide. The extremities are rounded, and there is a median cusp 
extending across the crown; on each side of the cusp, the face of 
the crown is slightly concave. The enamel is strongly but finely 
wrinkled. The tooth series terminates abruptly in a tooth of 
half the transverse extent of the penultimate. Length of space 
occupied. by penultimate and ante-penultiniate teeth M. .021 ; 
length of base of pART a; width of do. .024; elevation 
of crown, least .006; do. at c , 009. 
This species is larger than fice heretofore described, and the 
teeth are adapted for crushing harder bodies—having perhaps a 
use like those of Placodus or Pycnodus. It is called D. molaris. 
EOLOGY OF THE BRITISH Arctic EXPEDITION.—Geological 
investigation in the Polar regions is beset with difficulties of so 
grav character that very few collections have hitherto been 
brought home by Arctic explorers, and these have necessarily 
been meagre uring Sir George Nares’ expedition, however, 
a fact worth mentioning, se some s othar fine collections have 
been lost to science through the mishaps incident to Arctic trav- 
eling. The recently formed collections, and the results deduced 
from their study, were lately laid before the Geological Society. 
In working out the stratigraphical results, Captain Fielden 
has had the benefit of Mr. de Rance’s aid, and in the palæontolog- 
ical department that of Mr. Etheridge. The fundamental rocks 
_ * American Naturalist, 1868, May, p. 327. 
