52 



however, ranges up into the Meadow vale on the Credit. The remaining species 

 are either new or long-ranging. 



It will be seen from the above analysis of the fauna that the closest relation- 

 ships are with the Liberty as defined by the majority of authors or with the 

 Liberty and Lower Whitewater of Shideler. 



Although the relationships of the Streetsville are as stated above; never- 

 theless, the member differs greatly from the Liberty of Ohio. The predominant 

 fossils of the former are Bryozoa, and of the latter Brachiopoda. Many of 

 the characteristic fossils of the Liberty are entirely absent from the whole 

 Credit River section, such as Dinorthis subquadrata, Plectambonites sericeus, 

 Rhynchotrema capax, Strophomena planumbona, and Amplexopora granulosa. 

 In addition, the Streetsville member has yielded eight new species and three new 

 varieties which are almost entirely confined to it. 



In connection with the fauna of the Streetsville, it must be stated that Dr. 

 E. O. Ulrich, in a letter to the writer, records the occurrence of Modiolopsis 

 valida associated with Opisthoptera alternata and Modiolopsis concentrica. No 

 examples of Modiolopsis valida were found at this horizon, but Dr. Ulrich 

 identifies the species from the Prison Farm quarry in strata which are ascribed 

 to the Humber member of the Dundas formation. 



Meadowvale Member 



Columnaria Reef. — The Meadowvale member begins with the conspicuous 

 Columnaria reef, in which Columnaria alveolata, Tetradium approximatum, 

 and Stromatocerium huronense are very abundant. Columnaria calicina is also 

 present but is not so abundant as the foregoing species. Tetradium approxi- 

 matum assumes at times very large proportions, one specimen being found with 

 a diameter of 18 inches. In addition to the above coelenterates, the two 

 bryozoans, Rhombotrypa quadrata and Constellaria polystomella, are very 

 abundant. It is strange that these two species, which in other areas are found 

 in nearly all of the divisions of the Richmond, should be found only at this 

 horizon on the Credit. The following fossils, also, are found in the Columnaria 

 reef: Hallopora cf. onealli, Homotrypella hospitalis, Hebertella occidentalism Platy- 

 strophia clarkesvillensis, Zygospira modes ta, Byssonychia sp., Opisthoptera 

 fissicosta, Lophospira bowdeni, Lophospira tropidophora, Cyclonema sp., and an 

 indeterminable species resembling Fenestella. Foerste lists from this horizon 

 Calapoecia cribrijormis and small specimens of Streptelasma rusticum. The reef 

 varies in thickness from 18 inches to five feet and consists chiefly of limestone, but 

 thin bands of shale are also present, and in many cases the corals lie embedded 

 in shales. 



Upper Meadowvale. — From the reef to the top of the section, the rocks are 

 chiefly shale with a few beds of limestone and arenaceous limestone and shale. 

 The fossils occurring in these upper layers are: Hebertella occidentalism Platy- 

 strophia cf. clarkesvillensis, Rafinesquina alternata, Rafinesquina alternata sub- 

 circularis, Zygospira modesta, Homotrypella hospitalis, Clidophorus fabulus, 

 Byssonychia sp., Modiolopsis concentrica, Opisthoptera cf. fissicosta, Pterinea 

 demissa, and Whiteavesia pholadiformis . 



There is only one horizon above the Columnaria reef worthy of special 

 mention and that is at the 525-foot level at the very top of the section. Here 

 there are a few beds of limestone in which Hebertella occidentalis is exceedingly 

 abundant. Platystrophia clarkesvillensis, indeterminable species of Modiolopsis 

 and Byssonychia, and casts of Bryozoa are also found. 



