924 THE PALEONTOLOGY OF MINNESOTA. 



[Buoanoptls. 



resembles Protowarthia granistriata more closely in this respect than either Biicanella 

 trilobata Conrad sp., or Kokenia esthona. 



The longitudinal striation, unusual width and elevation of the slit-band, the 

 last feature producing an obscure tripartite character to the shell, seem to be the 

 principal characters upon which Koken bases his conception of Bucanella as distinct 

 from Bucania, which with him included Bucanopsis. These features he finds in his 

 B, esthona, Krause's B. substriatus and in several other Silurian and Devonian shells 

 which he assumes to be related to species upon which Meek founded Bucanella. 

 This assumption, however, is totally unwarranted, and in the absence of sufficient 

 evidence to prove his point Koken should not have charged Meek with an incorrect 

 description. 



The elevation of the slit-band in the group of species under consideration is 

 probably not of much consequence, though usually present. Its unusual width, 

 however, may be of importance but we see no way of utilizing it at present. The 

 extension of the revolving lines over the slit-band also seems to us to be of little 

 value. We came to this conclusion because they may be present in one and absent 

 in the other of two closely related species. For instance, in Bucanopsis textilis Hall 

 (not De Koninck sp.), of the Warsaw or St. Louis group, the slit-band seems always to 

 be without revolving lines, but in an undescribed form recurring in the Chester 

 group of Kentucky, and which can scarcely be distinguished, such lines are clearly 

 present. We find them also in B. leda Hall, while they are absent in the closely 

 related B. lyra Hall. Then they are developed again in some of the Carboniferous 

 species, notably B. marcouiana Geinitz, B. ellipticus McChesney, and B. montfortianus 

 Norwood and Pratten, the last belonging to the Bellerophon patulus group of species. 

 It seems to us, therefore, unreasonable to accord any more than specific importance 

 to the presence or absence of these lines. 



There is another assertion made by Koken to which we must take exception. 

 He says that B. esthona is "obviously a combination of the characters of the so-called 

 Euphemus and Bucania." This observation is so totally at variance with our own 

 opinion that we are almost at a loss to answer it except with a simple contradiction. 

 He is most assuredly far from the truth if he means to imply that the revolving 

 ridges of Euphemus, which we cannot for a moment doubt are really folds of an 

 extension of the inner lip, are in any way comparable with the spirally ribbed 

 external surface sculpture of Bucania and Bucanopsis. 



