934 



THE PALEONTOLOGY OF MINNESOTA. 



[Kaph Is torn Idle. 



lower lip also has become more strongly and constantly sinuate, causing a more 

 oblique aperture. The evolutional modifications, it will be noticed, are almost 

 exactly opposite in the two cases. As to Omospira, it was most probably derived 

 from Raphistoma, or from some unknown allied type. The relations and differences 

 existing between Raphistoma, Raphistomina and Euomphalopterus are clearly shown 

 by the figures in the accompanying cut: 



FIG. 5. Sketches illustrating the character of Raphistomina, Raphistoma and Euomphalopterus. a, 

 b, c, three views of Raphistomina lapicida Salter sp.; d, e, f, similar views, x 2, of Raphistoma peracutum, a 

 depressed but otherwise very typical species of the genus; g, h, i, similar views of Euomphalopterus alatus 

 var. obsoletus, n. var. The last is from the Niagara group near Waldron, Indiana, and is the only American 

 representative of this peculiar genus known. It differs from the European varieties of the species chiefly 

 in wanting the ridge which surrounds the umbilical cavity in those forms. The umbilicus in our variety 

 is also a trifle narrower than usual. 



Raphistoma, Hall, that long misunderstood and much debated genus, is now for 

 the first time since 1847 correctly interpreted, limited and placed. Justice demands 

 that Prof. James Hall, the author of the name, should be credited with having given 

 a diagnosis that is strictly correct and sufficiently detailed to satisfy even the pres- 

 ent requirements. He noticed and says distinctly that his Raphistoma has no band, 

 and this fact of itself should have been accepted as fully justifying a separation 

 from Pleurotomaria. Instead we find that authors have generally regarded his 

 genus as indistingishable from Scalites Conrad, and both as synonyms of Pleuroto- 

 maria. Salter,* it is true, gives Raphistoma, together with his Helicotoma and 

 Vanuxem's Ophileta, the rank of subgenera under Scalites (which he refers to the 

 lanthinidd), and distinguished them from Pleurotomaria because of the absence of 

 the spiral band. However, as we will show later on, Helicotoma and Ophileta are 



Canadian Organic Remains, doc. 1. p 10, 1850. 



