18 MUSEUM OF COMPARATIVE ZOOLOGY. [Feb. 
object of your efforts. It is of the utmost importance that a 
reference to our collections should in future afford naturalists the 
means of recognizing all the species which have been described in 
this country, not only by your cotemporaries, but also by your 
predecessors. 
“You know how difficult it has become to identify some of the 
species described by Say and Rafinesque, and unless proper care is 
taken in time to secure what remains of the tradition of the earlier 
American conchologists, the task may become hopeless. 
“Therefore I would urge that you make a beginning at once. 
To this end I would advise you to make an excursion to Phila- 
delphia as soon as convenient, and you can ascertain that you may 
receive there the necessary aid in your work. I have already once 
examined the remnant of Rafinesque’s collection, in the possession 
of the late Charles A. Poulson, but I wish you would go over the 
same ground, and not limit yourself, as I did, to the Naiades, but 
try to identify the other shells described by him. Next to this, 
I wish you would compare all the specimens of Say, Barnes and 
Ward that.may be preserved in the Academy of Natural Sciences. 
Mr. Binney, whose father was a correspondent of those gentlemen, 
may assist you in identifying some of their species, of which there 
may not be authentic specimens in your own collection. At the 
same time you should identify all the species of Dr. Binney which 
are in his son’s possession. 
“The next most important step would be the comparison of all 
the species described by Mr. Isaac Lea with those of the Museum. 
No naturalist in America has described and figured so large a num- 
ber of species of shells as Mr. Lea. By his untiring industry and 
perseverance he has brought to light an astounding variety of fresh- 
water mollusks from our extensive river system, entirely unsus- 
pected before; in fact, no one has made larger contributions to our 
knowledge of the American Naiades. It is therefore of paramount 
importance that we should obtain, at any reasonable cost, authentic 
specimens of all his species, whenever we have not ourselves speci- 
mens which can be identified with his. 
“This is a very extensive and laborious task, and I do not sup- 
pose that you can accomplish the whole during one visit to Phila- 
delphia; but you may get through with one family, say the 
Melanizx, the arrangement of which you have lately completed in 
the Museum, and make arrangements with him to return to Phila- 
delphia and complete the comparison whenever it may suit him to 
assist you in the investigation. As we have land and fresh-water 
shells in large quantities from localities from which Mr. Lea may 
