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pares the very allied forms of the amygdaliira group. 

 The true parvus seems not to occur in Florida, but in- 

 -Georgia, where the variety with more marked undula- 

 tions was named otherwise by Lea. 



I agree with Sim/pson in the synonymy of U. modio- 

 liformis and believe it necessary to join U. Prevostianus 

 Lea. Allied species are r. lienosus and teoerus, both 

 probably only varieties of one species, and which has an 

 other and angular form of the posterior extremity of 

 the female as it is the case of U. modioliformis. It seems 

 to me to be quite essential, to know of all species oi 

 Unio : the sculpture of the beaks and the difference oi 

 sexes as soon as there is any such dimorphisme. 



It seems to me that north american conchologists, 

 in accompanying Leas errors, are always much dis- 

 posed, to avaliie too much the value of the AUeghanies 

 as a faunistical separating barrier. The AUeghanies by 

 no means have such an importance as the Rocky Moun- 

 tains have, nor for fishes nor for Unios. We have nu- 

 merous species identic to both the sides of the AUe- 

 ghanies, and in Georgia we have as demostrated above 

 représentants of such characteristical groups as Unio 

 ventricosus, ovatus, clavus, circulus, lacrymosus, plicatus, 

 etc., are. In Florida th Unionid fauna is the same but 

 depauperated, having no Margaritana, but one Anodonta, 

 -and none of the types above cited from Georgia 



The Roky Mountains form a much more important 

 limit, as we have besides of the holarctic Margaritana 

 margaritifera the european Anodonta rostrata Kock called 

 An. nuttaliana Lea (1 > and 2 species of Unio, concernig 

 to which I am not in concordance with Simpson, judging 

 Unio oregonensis Lea, which he says to be allied to 

 luteolus, as a membre of the great number of sulcate 



(1) Synonymic are A. wahlamalensis Lea and califoriiiensis 

 Lea, but. A. oregonensis Lea and angulalus Lea are different 

 species- 



