650 SUPPLEMENT. 
Unio aztecorum, var. strebeli (p. 503). 
According to Simpson (loc. cit. p. 592, nota), the type of U. strebeli, Lea (in the 
U.S. Nat. Museum), is, without doubt, a young specimen of U. medeliinus. I am 
unable to reconcile this with the fact that the figure which Lea himself gives of his 
U. strebeli (Obs. Unionidae, xii. t. 51. fig. 131) is of considerably larger size than that 
of his U. medellinus (Obs. Unionide, ii. t. 12. fig. 34): the former measures 74 millim. 
long, 41 high, and 26 in diameter, the latter 57 long, 35 high, and 18 in diameter. 
Specimens labelled U. strebeli in Strebel’s own collection, now in the Hamburg 
Museum, are still larger, as I have already stated (anted, p. 503). As a rule, young 
examples of these bivalves are comparatively more compressed than old ones of the 
same species; but, according to the figures given by Lea, in U. strebelt the transverse 
diameter is considerably more than half the height (26:41), in U. medellinus about 
half the height (18:35). The shell described and figured by Lea as U. strebeli cannot, 
therefore, be a young specimen of U. medellinus. 
Unio popei (p. 504). 
Unio popei, Simpson, Proc. U.S. Nat. Mus. xix. p. 871 (1896) *. 
Again found in both the original localities, Rio Salado, Nuevo Leon, Mexico, and 
Devil's River, Texas, by the Biological Expedition of the U.S. Department of Agriculture; 
also in Kinney County, Texas, by Dr. Mearns’. 
Unio cuprinus (p. 505). 
Simpson (oc. cit.) distributes under three genera the forms which I have treated 
as varieties of U. cuprinus: U. cuprinus and U. metallicus as one and the same species, 
under Lampsilis (p. 572); U. persulcatus, U. calamitarum, and U. tabascoensis under 
Nephronaias (p. 596); and U. coloratus under Unio, section Elliptio (p. 700). If I 
am not utterly misled in my determinations by the specimens in the Berlin Museum, 
labelled by Dunker, Albers, and others, all these forms run one into the other, and 
belong to one species, which is rather variable in outlines, but constant in the sculpture 
and coloration. Simpson’s spelling “calimatarum” is without meaning: Morelet 
wrote “ calamitarum,” derived from calamita, a name given to a sort of frog or toad 
by different authors, or from calamus (calamites), reed-grass (he has also called an 
Anodonta, “ bambousearum”). According to Simpson’s bibliographical researches, the 
first-published specific name is metallicus, Say, preceding Lea’s cuprinus by more than 
six months ; both are equally descriptive of the species in question *. 
* In 1869 a Committee of the conchological section of the Academy of Natural Sciences of Philadelphia 
recommended that the date of the reading of Lea’s papers before the Academy should be taken as the date of 
publication (Am. Journ. of Conchology, v. p. 34); according to this rule, 
the name U. cuprinus would be 
preferable. 
