GUELPH FAUNA IN THE STATE OF NEW YORK I 2 1 



zoans, 4 crinoids, 19 brachiopods, 1 1 gastropods, 9 lamellibranchs, 24 cephalo- 

 pods, and 16 trilobites. And an exhaustive examination of the collections 

 would doubtless much increase the number. 



Of the granular varieties of rock, that which is nearest allied to the reef 

 rock is peculiarly notable for an abundance of crinoids. The locality near 

 Racine is preeminent in this respect. Upwards of 30 species have been 

 identified from this one locality. These are associated, as will be seen by 

 consulting the table, with a large number of corals, brachiopods, gastropods, 

 cephalopods, trilobites and a lesser number of other forms. 



The fauna of the compact strata is distinguished for the conspicuous 

 presence of the straight and curved cephalopods with comparatively few 

 associates. The cephalopods are abundant, as already noted, in the reefs 

 and crinoid beds, but are overshadowed by the number and variety of other 

 forms, while in the compact rock they greatly predominate. 



It appears then, (i) that upon the reefs there swarmed a vast variety 

 of life ; (2) that upon certain banks or shoal areas there was also great 

 abundance and variety, among which the crinoid family attained unusual 

 prominence ; (3) that over areas of submarine sand flats there either was 

 little life present, or, from the porous nature of the rock, it has been illy 

 preserved, and (4) that over the deeper areas, that deposited fine calcareous 

 mud, the gigantic cephalopods held sway. The counterpart of all this is to 

 be found among the coral reefs of today. 



These conditions in Wisconsin continued from Racine into the Guelph 

 time, as Chamberlin says of the Guelph (p. 377) : 



In its lithological character, in does not differ essentially from the 

 Racine limestone, being in general a rough, thick bedded, irregular dolo- 

 mite, usually quite free from impurities, and of buff, gray, or blue color. 

 The distinction between the two subdivisions is a paleontological rather 

 than a physical one. In the latter respect there is less difference between 

 these than either of the other members of the group. There was evidently 

 no marked change in the physical history of the region, but the same con- 

 ditions continued from the beginning of the deposit of the Racine limestone 

 to the close of the formation of the Guelph beds. In the interval, however, 

 the life underwent a change by the introduction of the species that charac- 

 terize the Guelph horizon. This introduction was gradual, so that many 

 localities show a mingling of the two faunas. 



In New York the Guelph period was still a time of coral reefs, and the 

 distribution of the peculiar fauna, characteristic of this reef in Ontario and 

 Ohio, shows that probably the entire shallow Guelph basin was more or less 

 studded with coral reefs. 



