114 THE NAUTILUS. 



(here let me say that I have traversed every inch of the shore of L. 

 Monroe, dredging in scores of places in the lake and adjacent 

 streams and never found a perfectly typical specimen of this species), 

 occultns Lea, and papyraceus Gould, the last a specimen loaned from 

 the Newcomb collection. When we finished, thousands of specimens 

 remained that could not well be placed with any of the groups. 

 These were divided into groups and further search made among the 

 various authorities at hand to discover their identity. After elim- 

 inating all possible, many interesting forms remained, represented by 

 large numbers of individuals. These we desired to classify and use 

 in exchanges, and names we must have for them. We reasoned thus : 

 The water system of South Florida is in no way connected with 

 Georgia or the States north, the rivers flowing northward instead of 

 southward ; many of these forms are found in isolated lakes or 

 ponds ; large numbers of our known species described by Lea, 

 Conrad and others from a single individual, sometimes a single valve 

 only and rarely more than a small suite being at hand ; some of the 

 oldest known species have never been found outside of the original 

 station. These facts justify us in erecting into species such well 

 marked forms as are well represented in these unknown lots. 

 Accordingly this was done and now I am censured for not having 

 given the matter sufficient study. Will those who claim to know, 

 tell us through the Nautilus how they arrive at such definite and 

 positive conclusions regarding the genuineness of some of my own 

 and other's species? Will the censor name the exact characteristics 

 of any species ? Information of this sort will be hailed with wild 

 delight by all working naturalists, and the name of the discoverer will 

 always be held in grateful remembrance by all lovers of science. We 

 wait. 



I believe there can be no safe middle ground. It is either true 

 that there is but one species in the family or else most of the 

 descHbed species must stand as good. 



In the U. S. the Anodon graduates by imperceptible stages into 

 the Margaritana and that into the Unio. 



We once found a lot of shells in a Pennsylvania stream that both- 

 ered us greatly, and the late Dr. Wesley Newcomb pronounced them 

 a cross between An. undidata Say, and U. pressris Lea. Exteriorly 

 they were the latter but interiorly the former. This suggests the law 

 of hybridization. Distinguished authorities tell us that members of 

 the same species only are fertile ; the crosses in some rare cares prov- 



