58 NEW YORK STATE MUSEUM 



diameter. It is also much more widely umbilicated and the outer volu- 

 tions embrace the inner ones for about one half their width. As the 

 large series of New York specimens are quite uniform in their relatively 

 high volutions, it seems to us that the specimen from Genoa O., repre- 

 sents another type and approaches Trematonotus chicagoensis 

 McChesney, which (in its restricted definition) possesses only low volutions 

 and a very wide umbilicus. 



Trematonotus alpheus is very nearly related to T. longi- 

 tudinal is Lindstrom, which has cylindric volutions, a like surface orna- 

 mentation and an equal degree of umbilication. It differs however in hav- 

 ing a relatively much greater expansion of the lateral peristome and shorter 

 outer lip ; and T. alpheus does not exhibit the distinct dorsal ridge of 

 the outer lip in continuation of the slit band, and the corresponding sinua- 

 tion of the margin of the outer lip. Lindstrom regarded his species most 

 nearly related to T. trigonostoma Hall & Whitfield, evidently 

 because only incomplete casts of the more closely related T. alpheus, 

 had been figured at the time of his study. 



The peculiar preservation of the majority of the specimens as molds is 

 evidently the same as in the Gothland material, for the principal figure given 

 by Lindstrom illustrates the same mode of preservation. Failure to prop- 

 erly interpret this figure led Koken to the misconception that it represents 

 the inside of the aperture, and he has stated, 1 in his elaborate research 

 Ueber die Entwickelung der Gastropoden vom Cambrium bis zur Trias, 

 that Trematonotus has on the aperture internal folds, which show no rela- 

 tion to the outside sculpture. Our material shows how easily this miscon- 

 ception could arise. The wrinkled sculpture is actually that of the outside 

 of the aperture, and the inside of the aperture was nearly smooth. 



We need not emphasize here the significance of the discovery of this 

 species in New York at a horizon corresponding to its occurrence in 

 Canada and Illinois. We fail to find the form cited among the Guelph 

 fossils of Wisconsin ; among the Racine fossils, however, there is listed 



'Neues Jahrb. Beilagebnd. 1888-89. P- 3 86 - 



