52 CASE. [VoL. XIV. 
South Dakota.! The description includes the carapace, verte- 
brae, limb bones, and pectoral girdle, which he regards as 
indicating a new genus and species, Archelon ischyros. Nothing 
is added to our knowledge of the morphology of the extinct sea 
turtles, except the presence of a row of neural plates. This 
point shows my conclusions as to their absence to have been 
an error. 
Mr. Wieland bases his new genus largely on the disparity in 
size between it and Cope’s specimens of Pvotostega, and on 
several minor differences in the vertebrae, scapulae, and cora- 
coids. The difference in size between two forms can rarely be 
used as a criterion for determining their generic individuality. 
For one accustomed to the great range of this feature in the 
fossil reptilia, and the persistent, though slow, growth through- 
out life of many recent forms, the use of this character seems 
attended with grave danger. The present paper was founded 
on two specimens of Protostega, one about half the size of the 
other, while Cope’s described specimen is intermediate in size. 
The “minor development of the smaller trochanter ”’ attributed 
to Archelon (p. 406), and the presence of “longitudinal depres- 
sions’ on the shaft of the proscapular process of the scapula 
(procoracoscapular), instead of a “rotund” outer edge (p. 404), 
are, with characters of a like nature, features which might be 
readily produced or destroyed by the compression from which 
all specimens from the Kansas chalk suffer. 
Mr. Wieland further speaks of the greater breadth of the 
carapace of Avchelon as compared with Protostega. His con- 
clusions are based on the calculations of Cope and Hay which 
I have shown above to be erroneous. His specimen has a 
length of 3.52 meters, and a breadth of 2.25, a little less than 
two-thirds, while mine is a little over one-half as wide as long. 
Archelon must be considered as a synonym of Protostega, and 
even its specific separation remain an open question. 
December 14, 1896. 
1 Archelon ischyros : a New Gigantic Cryptodire Testudinate from the Fort Pierre 
Cretaceous of South Dakota. Am. Jour. Sci., vol. ii, December, 1896, p. 399, I PI. 
