FRESH WATER AND LAND SHELLS. OL 
procure good specimens of both, will, on a critical examination, declare them to be differ- 
ent from each other and distinct from fuligiata. 
In the very learned and elaborate work of the late Dr. Binney, “Terrestrial Air-Breath- 
ing Mollusks of the United States,” he takes occasion to state his strong disapprobation 
of the use of personal names for species in natural history, and at the same time points 
out a case where he considered it had been carried, to an abuse by a naturalist of this 
city. I wish simply, in answer, to give an opinion on the subject, first premising, that 
Dr. Binney had himself, in at least two instances, applied personal names to his own 
species, few of which he made, committing a graver error than those who do not disap- 
prove of the use of personal names. 
There are several reasons, in my opinion, why they may be used: 
Ist. Most of the great naturalists, for nearly one hundred years, have used them with- 
out hesitation; and the most distinguished of modern writers have sanctioned the example 
by following it; as Lamarck, in Helix Bonplandii, &c.; Ferussac, in Helix Richardii, &c., 
as well also other eminent writers in various branches of natural history. 
2d. It is a good substitute, where a well recognised descriptive name cannot be applied, 
which is often the case. 
3d. It is an honourable acknowledgment of services performed by co-labourers in the 
field of science, and it is a gratification due to ardent collectors, who labour for the man 
of science at a distance, and often in parts of the world subject to disease and other 
dangers. 
Some very distinguished naturalists have gone much beyond the simple use of proper 
names for species, for they have applied them even to genera. For instance, Lesueur’s 
genus Macluria; Tremenville’s genus Rissoa; D’Orbigny’s genus Acosta, &c. &c. 
In botany, personal names thus applied to genera have been most extensively used. 
In zoology I do not consider this necessary or desirable, but I do think there is not only 
a convenience in using such names for species, but sometimes almost an imperative 
necessity for it. Ip very extensive genera, where many hundred species abound, as in 
the genera Unio, Melania, Conus, &c., &c., it would be impossible to obtain descriptive 
names for all. 
