THE NAUTILUS. 7 



him in Paris and identified his collection and who had had ap- 

 parently before him anthentic examples of both undatus and trigonus, 

 came to the same conclusion. He disregarded Lea's reference of 

 undatus to obliquus Lam. and considered that species to be some- 

 thing quite different. 



In 1849 the Western Academy of Natural Sciences of Cincinnati 

 published a " Catalogue of the Unios, Alasmodontas and Anodontas 

 of the Ohio River and its Northern Tributaries." It does not appear 

 who compiled it. In this list undatus is recognized as a valid species 

 with four synonyms ; i. e., caridiacea Say, mytiloides Rat., obliqua 

 Lam, and pyramidata Lea. Trigonus is doubtfully referred to ftavus 

 Raf., of which rubiginosus Lea is considered a synonym. 



Kuester (Conch. Cab. Unio, p. 58, pi. XIII, fig. 4, 1852) differs 

 from every other writer in his disposition of the species. He con- 

 siders it a white-nacred form of Obovaria retusa Lam. His figure 

 represents a shell quite different from undatus in shape, with tlie sur- 

 face heavily sulcate transversely. 1 have 'never seen anything like 

 it and whatever else it may be, it certainly is not the undatus of 

 Barnes. I have been unable to find any reference to this figure in 

 Simpson's Synopsis. 



In 1853 Conrad (Pr. A. N. S. Phila. VI, pp. 243-269) published 

 an elaborate " Synopsis" of the Naides. In this, undatus and trigonus 

 are recognized as distinct species and in a note the author gives what 

 he considers the distinguishing characters of each. He emphatically 

 repudiates the reference of undatus to Lamarck's obliquus, which he 

 considers has priority over one of Lea's species. 



This was the last revolt against the arrangement adopted by Dr. 

 Lea in 1833. 



After this time the preponderating influence of Dr. Lea in deter- 

 mining the nomenclature of the North American Unionida was suf- 

 ficient to impress his opinion as to the standing of Dr. Barnes' species 

 upon collectors, and the name practically disappears from the litera- 

 ture except as a synonym of obliquus Lam. 



Simpson in his recent Synopsis (1900) follows Lea in his disposi- 

 tion of the species. 



I. 



What is the Unio undatus of Barnes ? 



There is no real difficulty in determining this question, if due con- 



