42 The Ohio Naturalist. [Vol. XIII, No. 2,. 



When Prof. Arthur M. ^vliller visited the exposures at the 

 extreme northeastern end of the railway" line crossing Goat island, 

 he was impressed with the Curdsville facies of the fauna included. 

 He found Carabocrinus vancortlandi, Cleiocrinus regiiis, and 

 Glyptocrinus ramuJosus, to which have been added more recently 

 Reteocrinus alveolatus and Cyclocystoides halli, a typical Kirkfield 

 fauna. Among the bryozoans collected at this horizon Dr. E. O. 

 Ulrich identified provisionally Batostoma wincheJli, Bythopora cf. 

 alcicornis, CaUopora multitabulata, Eurydictya multipora. Homo- 

 try pa minnesotensis, MonticuUpora {^) cannonensis, Rhinidictya 

 minima, and Rh. mutahilis. Apparently there is an admixture of 

 Black river with Trenton species, but possibly the real explana- 

 tion is merely the greater vertical range of various species hitherto 

 not found above the Black river. 



The total thickness of the strata to be assigned to the Curds- 

 ville bed is unknown. From the lowest strata seen on Goat island 

 to the highest strata containing an abundance of the columns of 

 Glyptocrinus ramulosus, the interval is nearly" 30 feet. The 

 Carabocrinus vancortlandi layer is about 7 feet above the base of 

 this section, and most of the other crinoids and cystids occur about 

 11 feet above this level. Stromatocerium is rare in the layer 

 immediately overlying the upper Glyptocrinus horizon, but becomes 

 common at a higher horizon which is exposed along the southern 

 margin of Goat island. Possil^ly 20 feet would l^e sufihcient to 

 cover this interval, and an equal interval might account for the 

 strata intervening between this abundant Stromatocerium horizon 

 along the southern edge of Goat island and the lowest strata 

 exposed along the shore in the eastern margin of Little Current. 



6. Trenton Exposures at Little Current, on Manttoulin 

 Island, including Collingwood Formation. 



Immediately at water's edge, east of Little Current, the 

 following bryozoans were collected and submitted to Dr. E. 0. 

 Ulrich: Arthoclema billingsi, CaUopora multitabulata, Dekayella 

 trcntonensis, Eridotrypa mutahilis. Mcsotrypa injida, M. cf. whit- 

 eavesi, MonticuUpora arborea, Prasopora simulatri.x. and Rhini- 

 dictya fi delis. The fauna as a whole impressed Dr. Ulrich as 

 resembling that in the Ncmatopora horizon in the upper Prosser. 

 While some of the species are found also in the Wilmorc, these are 

 forms which occur also in the upper Prosser, while conversely no 

 forms are seen here which occur only in the Wilmore. A small 

 s]3cciiTicn of Strophomeua and nimicrous specimens of Rhyncho- 

 trema inaequivalve occur at the same horizon. 



If the abundant Trenton fauna found in the white limestones 

 northwest of Collingwood, on the lake front, find any equivalent 

 in the Mantoulin area, this must lie somewhere between 20 and 30 

 feet above the lake in the section exposed east of Little Current ^ 



