oS { APRIL, 
_W. Stimpson, who cites Prof. Agassiz’s MSS., that they do not differ essentially 
in their modes of division. Mr. Lea farther remarked, that. our knowledge of 
the structural differences of the soft parts of these animals, he. thought, was not 
sufficiently advanced to found a perfect and permanent system. That such a one 
would be instituted he had no doubt, as he had expressed himself in 1838, ina note 
on Anodonta Blainvilliana, in the second edition of his Synopsis, p. 31, and he 
trusted, that the able physiologists above cited would continue their investiga- 
tions; but he was disposed to think that, until zoologists had examined carefully 
the soft parts of most of the existing numerous species,—tke exo-skeletons* 
(so to call them) of which have only come under our notice—the facilities which 
a good system ought toafford, cannot be reaped by a partial anatomical know- 
ledge, which does not now embrace probably one eighth of the ascertained spe- 
cies of the family. Besides, he was not at all disposed to think, that we can en- 
tirely dispense with the aid we find in the various characters of the exo-skele- 
tons in making out subgroups. » They often, indeed, afford striking and obvious 
differences, which the eye schooled with but little experience, can with facility 
and certainty detect, and which if happily grouped by an experienced eye may 
greatly aid the student. These considerations had induced him still to retain 
nearly the same divisions in the new edition of the Synopsis, which had been 
used in the last one. . 
. April 13th. 
Vice President BripGss in the Chair. 
Letters were read 
From the Lyceum of Natural History, of New York, dated March 
24, 1852, acknowledging the receipt of a copy of the ‘ Notice of the 
Academy,’’ recently published. 
From Commodore Perry, dated New York, April 9, 1852, addressed 
to Dr. Ruschenberger, expressing his desire and intention to comply 
with the request of the Academy to make scientific researches in the 
East Indies, during the cruise of the U. 8. Squadron on that station. 
Dr. LeConte read a paper entitled, “‘ Remarks on some Coleopterous 
Insects, collected by S. W. Woodhouse, M. D., in Arkansas and New 
Mexico,’ which was referred to Dr. Leidy, Dr. F. Beck, and Dr. Rusch- 
enberger. 
Dr. Zantzinger presented a paper from Mr. Charles Girard, of Wash- 
ington, entitled, “ Observations on the North American Astaci, by 
Charles Girard ;” which being intended for publication, was referred to 
Dr. Bridges, Dr. LeConte and Dr. Leidy. 
Dr. Hallowell read a paper describing new species of Reptilia from 
Western Africa ; which was referred to Dr. Woodhouse, Dr. LeConte 
and Mr. Lea. | 
Mr. Lea read a note from Wm. H. Prescott, Esq., dated Boston, 
April 8, 1852, accompanying his donation of the rare work “Registro 
trimestre,’’ announced this evening. 
On motion of Mr. Lea, the thanks of the Society were unanimously 
presented to Major LeConte for the valuable donation announced this 
evening, of his entire herbarium of North Americaa Plants. 
_ * Forming the calcareous coverings and fulcra for muscular fibres, as well as protec- 
tion from exterior forces, 
