62 THE NAUTILUS. 



The first species to be named was the plicatus. Although 

 that Thomas Say described it in Nicholson's Encyclopedia, was 

 an easily ascertainable fact, Dr. Lea persisted throughout his 

 life in denying this, and he credited the species to LeSueur ; an 

 error in which he has been largely followed. 



Say's type came from Lake Erie, and it has been claimed 

 therefore that his species is really the flattened form widely 

 known as undulatus. But in 3830 Mr. Say wrote the " plicatus 

 is a species with very prominent umboes." Therefore the pli- 

 catus (s. s. ) is that form which, as Barnes wrote, "can stand 

 on end." The more common form of the same species which 

 has flattened umboes, is very generally called undulatus Barnes. 

 This is an error of nomenclature for two distinct reasons. The 

 earliest name for this form is costata Rafinesque. The descrip- 

 tion of costata has been said to be inadequate, but without 

 good reason, for Rafinesque' s figure is unquestionably that of a 

 plicate shell. His statement that its "disc is flattened" pre- 

 cludes the plicnta, (s. s. ) and the statement that the "animal 

 is yellow" excludes the multiplicatus. 



The two forms above named constitute a single species, con- 

 nected by myriad links. The third form is readily distinguished 

 by its umboes being covered with literations. It is widely but 

 erroneously called heros Say, or multiplicatus Lea, neither of 

 which names should be used, since either of them have been 

 preceded by at least two (if not three!) names. The earliest 

 name is almost certainly peruviana Lamarck. But because of 

 ambiguity this name cannot be used. 1 Another name is the 

 undulatus Barnes, almost universally applied to the costata, but 

 is without doubt the heros Say! Barnes' statement among others, 

 that its "disc is tuberculate below the beaks" almost alone 

 proves this contention. As in the case of peruviana, the iden- 

 tity of undulatus has been thoroughly confused by authors, 

 about half identifying it with heros, the others with costata. 



Luckily there can be no doubt concerning the identity of the 



1 Lea stated that Lamarck's Unio peruviana was what has commonly been 

 known as U. plicatus. This identification is entirely borne out by the figure 

 n Encyclopedie Methodique, cited by Lamarck EDS. 



