LATER TERTIAEY (MIOCENE AND PLIOCENE). 823 



2. The Harrison heds. — These are well shown in the bluffs of all the small streams that head 

 near the summit of Pine Ridge, in the vicinity of Harrison, Nebr. They are also known to cover 

 a considerable area to the east, west, and south of that village, extending well into the State of 

 Wyoming. They are composed of about 200 feet of fine-grained, rather incoherent sandstones, 

 permeated by great numbers of siliceous tubes arranged vertically rather than horizontally. 

 They are further characterized by the presence, often in the greatest abundance, of those 

 peculiar and interesting but as yet not well understood fossils known as Daemonelix, and by a 

 considerable variety of fossil mammals belonging to characteristic Miocene genera. They 

 immediately and conformably overlie the Monroe Creek beds and pass insensibly into them. 



Osborn ®^^™ distinguished the upper Miocene, comprising the Procamelus zone, 

 and the "latest Miocene or first phase of the Pliocene," the Peraceras zone. He 

 gave an extended homotaxis and synonymy. 



K 18. LONG ISLAND. 



Veatch^^" mentions a possible occurrence of Miocene strata on Long Island as 

 follows : 



In the Long Island region and in the New Jersey region the Miocene sediments were 

 deposited under similar conditions, and as these two areas have been subjected to the same 

 forces, except glacial action, their distribution in both should be similar. The only bed thus 

 far seen on Long Island which is regarded as possibly Miocene is a thin bed of "fluffy sand" 

 which Mr. G. N. KJnapp recognized in the upper part of the Melville section, and which is the 

 counterpart of certain sands occurring in the Miocene of New Jersey. A comparison of the 

 sections indicates that if this structure is normal, and there is every reason to believe it is, a 

 Miocene outlier should be expected at this point. The same evidence shows the absence of the 

 Miocene above sea level on southern Long Island, except possibly along a portion of the South 

 Fluke. This line of argument is important, for it shows that the Tertiary deposits can not be 

 expected on the north shore any more than in the Hightstown Vale in New Jersey, and that 

 the occurrences on Long Island are probably limited to erosion outhers, with the embed beneath 

 the Atlantic. 



K 19. MARTHAS VINEYARD AND NANTUCKET. 



Dall^^ carefully examined the meager occurrences (too small to appear on 

 the map) of Miocene strata on the islands of Marthas Vineyard and Nantucket and 

 the collections which had been made from them and reported lists of species upon 

 which he comments as follows : 



It will be observed that this is a distinctly northern assemblage; any of the species might 

 be at home in the waters about Gay Head to-day, as far as we can judge by analogy in the case 

 of extinct species. , 



As regards correlation with the divisions of the southern Miocene it may be said (1) that 

 the Gay Head Miocene is Chesapeake and not older; and (2) that it belongs in all probability 

 to the upper part of the Chesapeake, certainly not lower than the- St. Marys fauna, and prob- 

 ably between that and the Yorktown beds. 



For a description of the strata see Chapter XV (pp. 682-683). 



In regard to the Pliocene, Dall says that a small collection of shells (for list 

 see the work cited) taken from a "layer of sand unconformably overlying the 

 Miocene" appears to belong to a "more recent fauna than the Miocene and may 

 perhaps be regarded as Pliocene." 



