Clarke — The Naples Fauxa. 



35 



is fully relieved of entanglements with the fauna of the west, it has been 

 termed the Otselic fauna.* 



East of the Ithaca meridian, in Cortland and Chenango counties, the rock 

 section above the Tully limestone consists of, first, a few feet of black Genesee 

 slate essentially without fossils ; then a mass of sandy shales and flags, from 

 250 to 300 feet in thickness. These strata are almost devoid of fossils but 

 those thus far found indicate some relationship to the Naples fauna. Professor 

 C. S. Prosser has recently called attention to the fact that to these strata as 

 exposed at Sherburne, in the upper Chenango valley, the late Laedxer 

 Vaxuxem applied the term " Sherburne sandstones." Prosser has, further, 

 demonstrated the persistence of these beds westward into the Ithaca section, 

 and proposes, with these excellent reasons, to recall this early name. West 

 from Tompkins county this division soon loses value. Above the Sher- 

 burne sandstones appears the series of arenaceous shales to which the term 

 Ithaca group has been applied. We have noticed above, that the fauna of 

 these beds is, in general, a reproduction of the Hamilton fauna below, less 

 rich in species, indeed, but with few that had not already been in this province 

 during Hamilton time. Some forms unknown in the Hamilton fauna or modi- 

 fied expressions of Hamilton species are introduced with these sediments. 

 Thus, for example; L&ptmna rhomhoidalis, a species not known in the Hamilton 

 fauna, occurs here ; certain forms of lamellibranchs which are but mutational 

 expressions of a Hamilton specific type, Actinopteria Boydi, characterize the 

 horizon. The fauna becomes gradually weaker in Hamilton traits as it con- 

 tinues upward in the rocks and the later appearance of the species Spi/rifer 

 mesastrialis marks a change of expression, this shell becoming thereupon the 

 leading index fossil in the faunas of the upper strata. 



In passing still further eastward a new lithologic and palaeontologic 

 element enters into -the composition of the Portage group. Approaching the 

 Chenango river we meet with a considerable thickness of red and green shales 

 and sandstones bearing, not infrequently, fish remains, and, in isolated localities, 

 the Umo-like fossil, A.mnig&ma GaUMUetisis^ anux. (sp) . This is the Oneonta 

 group, whose position is above the lower Otselic flags and perhaps the lower 

 portion of the upper Otselic flags, but which, for the most part, seems to replace 

 in this region the latter formation, the two passing into each other as synchronic 



*It would be a convenience in terminology if we had a term to express precisely the time significance of a fauna so 

 peculiarly placed as is this typical Portage fauna. Here is the fauna of a sharply defined province clearly set apart from 

 those of contiguous synchronic provinces. It would be an inexact u&e of a term to express its duration in Prof essor Buckman's 

 word Hemera, for the hemera of Manticoceras intumescens must mean the entire lapse of time represented by Portage 

 sediments everywhere, while in eastward sections of these sediments outside the boundary of the Naples province, Mantic. 

 intumescens and its peculiar organic associates are not present. The term needed is one which will express at once the time 

 unit and the geographic restriction of the fauna, one which will specify the duration of a particular faunal province, 

 as one should say, the Zoehemera of ilantic. intumescens. 



