Grabau — Faunas of the Hamilton Group. 



.329 



(which is probably incomplete as far as the rarer species are concerned) 

 wanting in the limestone at Eighteen-mile creek, this being Lyriopecten 

 suborbicularis (=L. orbiculatus)^ (which has been recorded from Eighteen- 

 mile creek). 



Of the fossils recorded from the rock from five feet above to four feet 

 below the Encrinal limestone, the following species do not occur in the 

 Encrinal of Eighteen-mile creek: a. Bellerophon leda. b. Pleurotomaria It/ys. 

 c. Cypricardiiiia identa. d. Pahroneilo feounda. e. Spirifer divaricatusi 

 f. Atnjpa reticularis, g. Polypora latitruneata. h. P. undulata. i. Oriho- 

 ceras exile. k. 0. nimtiurn. 1. Plev/rotomaria triJix. m. Mbdidmorpha 

 macilenta. n. Liopteria greeni. o. Goniophdra truncata. p. Aviculopecten 

 exactiLs. q. Dielasma Romingeri. r. Crania HamiltoiiicB. s. Trematospii'a 

 hirsutd. 



Of these a, b, k and g are known only from the lowest beds of the group 

 at Eighteen-mile creek, while e, g, h, m, n. a and s are unknown at Eighteen- 

 mile creek. Most of the others occur either immediately below of above the 

 Encrinal limestone at Eighteen-mile creek. 



It seems that we are thus justified in regarding the Encrinal limestone as 

 a continuous bed throughout the western part of the State of New York, 

 representing a uniform condition of sea bottom, purity of water, and physical 

 conditions generally, thus favoring the dissemination of species which probably 

 had a local origin. It also furnsshed the conditions favorable for the gradual 

 migration of faunas, from localities which had become unfavorable to their 

 existence to those in which their normal environment had become established. 



An examination of the fauna of the Lower shales of Livonia, reveals its 

 relation to the Marcellus fauna. This is especially true of the lower 147 feet, 

 as noted by Luther and Clarke, in which Marcellus species predominate. In 

 fact it seems to me, that these shales should be classed with the Marcellus, at 

 any rate as transition beds. The eighty-four feet of shale overlying these 

 beds, while exhibiting their Hamilton character in their fossils, nevertheless 

 contain many species which have passed upward from the underlying shales, 

 and are also found in the typical Marcellus shale. Eliminating these from 

 the recorded fauna, there remain the following species, which are distributed 

 through the eighty-four feet of shale below the Encrinal band : 



Modiomorpha subalata. c 

 *Paracyclas lineatus. rc 

 Aviculopecten princeps. rc 

 Palseoneilo fecunda. rc 



