28 NEW YORK STATE MUSEUM 



FEET 



undetermined species of Chonetes, and two of Rhynchonella, with R. acutipli- 

 cata, Leptocoelia concava, L. flabellites, Eatonia peculiaris, Rensselaeria 

 ovoides, two undetermined species of Spirifera, with S. arenosa, Atrypa reticu- 

 laris, Athyris laevis, two undetermined species of Modiolopsis and two of 

 Avicula, with undetermined species of Murchisonia, Pleurotomaria, Loxonema, 

 Orthoceras, Phacops, and Proetus, with Dahiianites pleuroptyx ... cqo 



800 



The entire volume of these Upper Silurian limestones would thus be about 2000 feet. 

 They occupy the whole of the promontory of Cape Gaspe, which extends from the main- 

 land for a distance of about 7 miles, with a breadth of no more than seven-tenths of a 

 mile ; except at its junction with the lowland extending to Cape Rosier, where it gradually 

 assumes a greater breadth. They skirt the northeast bank of the northwest arm of 

 Gaspe bay, and the left bank of Dartmouth river ; constituting a range of mountains, some 

 of whose summits, according to Bayfield, are about 1500 feet high. From Little Gaspe, 

 they are flanked by a strip of the succeeding formation, the junction of the two being 

 seen in Little Gasp6 cove. About 17 miles above Little Gaspe, these limestones cross the 

 north branch of the Dartmouth, upwards of 2 miles from the mouth of the tributary ; on 

 which a partial section, directly across the measures, presents a thickness of 1800 feet. 

 At the bottom of this, there are interstratified layers of chert, which have not yet been 

 observed at Cape Gaspe. 



The determinations of fossils appearing in this table were provisionally 

 made by Mr Billings, who afterward described in some fulness 42 species of 

 the higher beds but perfected his determination of the species of the lower 

 beds, 1-7, in 10 cases only. 



The passage of these beds from bottom to top, one into the next, is 

 altogether gradual and without interruption. In a general survey of the 

 great series of limestones, the lithic change is expressed in a tendency 

 upward to greater purity of limestone and chert deposits. With this 

 increase of purity the fauna becomes much more prolific and the upper beds 

 redound in fossils while in the lower divisions they are relatively rare. The 

 intermediate divisions from 2 upwards to 5 are comparatively barren while 

 in I more species are to be found. We have felt obliged to base any 

 subdivision of these 2000 feet of limestone chiefly on data that we have 

 ourselves been able to bring together. One can not be guided here entirely 

 by the determinations of fossils in Logan's scheme, for there are in his lists 

 suggestions of species which Billings in his final report failed subsequently 

 to record and our own collections contain many forms which are not indi- 



