960 THE PALEONTOLOGY OF MINNESOTA. 



LLophospira 



of doubt respecting the proper selection of the essential from the non-essential 

 among the exceedingly diverse characters exhibited by the original type of the 

 genus, M. coronata Goldfuss and its numerous varieties. We will say positively, 

 however, that none of the preceding genera can properly be united with Murchi- 

 sonia. Indeed, we are anything but satisfied that M. coronata is a true member 

 the Pleurotomariid.ee, and it appears that Koken felt more doubt on this point 

 than he expressed in the remark (op. cit., p. 367) that "the method of growth, 

 the rapid enlargement of the first volutions and other peculiarities remind of the 

 PyramidellidcB." On the same page he says also, in speaking of M. coronata and 

 varieties, "it is just this type that impresses me as though it did not belong with 

 the other Silurian, Devonian and Carboniferous species that are called Murchisonia." 

 With a few exceptions, we have seen specimens of all the American species which 

 have been described as of Murchisonia, and are quite prepared to maintain that 

 strictly speaking the genus is not represented among them. The continued use of 

 the genus for American species therefore is not justified except as a provisional 

 receptacle for those which, because of insufficient knowledge of their characters, 

 cannot yet be referred to their proper positions. 



We had intended to add remarks on De Koninck's Ptychomphalus, Gosseletia, 

 Pithodea, Agnesia, Rhineoderma and Baylea, and (Ehlert's Gyroma, Platyloron and 

 Stenoloron, (all proposed since 1880 as divisions under Pleurotomaria), but a lack of 

 space makes it necessary that their consideration be postponed to some future 

 opportunity. It may be well, however, to state here that each of these divisions 

 embraces species genetically distinct from those in the others and that, while they 

 will have to be redefined and their contents revised, none is likely to prove 

 entirely useless in the classification of the future. As to Pleurotomaria, De France, 

 if the genus is confined between reasonable limits, it is not recognizable among the 

 Paleozoic species known to us, nor are the sections Talantodiscus, Pyrgotrochus, 

 Perotrochus and Entemnotrochus, proposed by Fischer in 1885. The same is to be 

 said of Chelotia, Bayle, and Crypta>nia and Leptomtir/a, of Deslongchamps, which are 

 variously recognized as sections, subgenera, or as distinct genera. 



Genus LOPHOSPIBA, Whitfield. 



Lophospira, WIHTFIELD, 1886, Amer. Mus. Nat. Hist., vol. i, p. 312. 

 Jfurchisonia and Pleurotomaria, of authors. 



For generic characters see page 



As here understood and described this excellent genus constitutes perhaps the 

 most important of all occurring in the Lower Silurian. The species are numerous, 

 some have comparatively an extended geological range, and most of them are to be 



