1889.] Zoology. 1099 
Tursiop tursio, T. gillii, Delphinus delphis, Prodelphinus euphrosyne, 
P.plagiodon, P. longirostris, Tursio borealis , Lagenorhynchus acutus, L. 
albirostris, L. obliquidens, L. thicolea, Phocana cmnmunis, Ph. dallii, 
Grampus griseus, Globiocephalus melas, G. brachypterus, G. scammoni, 
Delphinapterus leucas, and Monodon monoceraus. Probably the above 
list will be extended, as these forms are largely cosmopolitan in their 
The Relationship of the Genus Dirochelys. — This tortoise 
was for the first time described by Latreille, from manuscript notes and 
drawings of Bosc, under the name of Testudo reticularia ; the year after, 
Daudin described it as T. reticulata. Agassiz established the genus 
Dirochelys for the tortoise, but he did not give any characters. He 
placed it in a sub-family of the Emydinidae under the name of Diro- 
chelyoidje (Agass., Cont. N. H. U. S., p 441). Boulenger (Cat. Tort., p. 
75) considers it a species of Chrysemys, and places it between Chr. dor- 
salia Kg. and Chr. troostii Holb. 
For a long time I knew only shells of this species. They at once 
proved the generic distinction from Chrysemys. The neurals were 
broader than long, a condition never found in Chrysemys ; besides, the 
rib-heads were enormously long, very much like those in Chelydra and 
Bmys blandijigii Holb. 
It was only a short time ago that I could examine the skull of a 
specimen in the Smithsonian Institution through the kindness of Dr. L. 
Stejneger and Mr. F. A. Lucas. 
The skull resembles very much that of E. blandingii. It has the same 
lower jaw, the same long postorbital part of the head, and the alveolar 
surface without median ridge. The interorbital space is still narrower, 
than in E. blandingii, forming less than one-half the diameter of the 
orbit. A comparison between Emys orbicularis L., Emys blandingii 
Holb., and Dirochelys reticularia Latr., shows that all three belong to 
different genera, and that Dirochelys is very much nearer to E. blan- 
dingii \}cvzxv to E. europcea. 
I give now the generic characters of these three forms. 
Emys Dum. 
Frontals excluded from orbit ; plastron united to carapace by liga- 
ment, and more or less distinctly divided in the adult into two lobes 
between hyo- and hypoplastra ; entoplastron intersected by the humero- 
pectoral suture. Rib-heads short as in Clemmys. 
Type, Emys orbicularia, L. 
Emydoidea, Gray (name only.) 
