1852. ] 35 
nication from Dr. Ruschenberger, dated Philadelphia, Feb. 18, 1852, 
in reply to the letter from the committee, enclosing a copy of the Reso- 
lutions adopted at the last meeting in relation to his ‘ Notice of the 
Academy.”’ 
Dr. Leidy directed the attention of the members to several fossils lying on the 
table, which belong to the cabinet of the Academy. 
One of them is a lumbar vertebra, without the epiphyses, and with the trans- 
verse processes and neural arch broken off, obtained from the Miocene of Vir- 
ginia, and presented by Mr. T. Conrad. It belongs to a species of Delphinus, 
most probably extinct, for which the name D. Conradi is proposed, in honor 
of one who has done so much in American Paleontology. The epiphysial extre- 
mities of the vertebral body are pentahedral. 
Length of vertebral body, : 3 : 24 inches. 
Breadth of epiphysial extremities, ° 3 ; Iguns 
Breadth of base of transverse processes, ‘ é es GS 
The other specimens consist of an entire dermal scale and the half of a second, 
from the Green Sand formation of Mount Holly, New Jersey. These belong to 
some Crocodilian reptile of large size. ‘They are deeply sculptured, but possess 
no carina, as in the existing Crocodiles. Possibly they may belong to the Sau- 
rian, characterized from some vertebre under the name of Cimoliasaurus magnus* 
Leidy, but at present I prefer referring them to a new genus and species under 
the name of Thoracosaurust grandis. 
Long diameter of the entire scale, : : . 34 inches. 
Short ce e e es e e 3 66 
Greatest thickness, : : 4 C : 7 lines. 
Mr. Langstroth made a few observations on the specimens of royal 
cells of the Bee, presented by him this evening. 
Dr. Le Conte offered the following observations : 
On the Difference between Primordial Races and Introduced Races. 
A want of power to discriminate between permanent varieties developed in 
species and primordial forms, has been a prolific source of confusion in all dis- 
cussions regarding the plural origin of species. I propose to examine here into 
some differences which, so far as Iam able to learn, will form a certain basis for 
this distinction, so much to be desired; and which, should they be found, on far- 
ther examination, to have the universal character which I am inclined to give 
them, may have the effect of saving the world much of the muddy philosophy, 
which seems to be the favorite style of ethnological writers. 
The principle which I am about to lay down, is founded on the unchangeability 
of certain characters, throughout an entire genus; these characters are connected 
with the structure of the external parts, and may seem at first to be of but slight 
importance, yet generally, on close examination, they will be found more or less 
intimately connected with the functions which the animal is destined to perform 
in the system of nature. 
Now, it is a singular fact, that all the varieties of domestic animals and plants, 
which can be clearly shown to have originated in unmixed breeds, differ from their 
parent stocks by characters which, except in the case of these, so to speak, artifi- 
cial varieties, are unchangeable in the genus. ‘Thus, these artificial varieties 
would seem to differ from their parent stocks, not by characters which are of 
specific value, but by those which are of incomparably greater importance, and 
which, if not accompanied by identical organization in all other organs, would 
widely separate the beings-which possess them from their parents. In many 
* Proc. Acad, Nat. Sei. vol. v, p. 325. { Seng a coat of mail. 
