58 [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, in a note 

 on Anodonta BlainviUia?ia, in the second edition of his Synopsis, p. 31, and he 

 trusted, that the able physiologists above cited would continue their investisa- 

 tions; but he was disposed to think that, until zoologists had examined carefully 

 the soft parts of most of the existing numerous species, the exo-skeletons* 

 (so to call them) of which have only come under our notice the facilities which 

 a good system ought to afford, 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. 



Ajpfil loth. 

 Vice President Brides 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. S. 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 evenine:. 



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 American Plants. 



Forming the calcareous coverings and fulcra fur muscular fibres, as well as protec- 

 tion fi-om exterior forces. 



