Handbook of Paleontology 335 



region the "Crinoidal" limestone, "Lockport Encrinal" 

 marble and "Lower Niagara" limestone, and is now 

 known as the Gasport limestone (Kindle '13). The fauna 

 of the Lockport dolomite (exclusive of the Guelph fauna) 

 is not an abundant one. There is the normal Lockport 

 fauna, derived from the Rochester fauna and much more 

 common in the argillaceous facies, and the crinoid fauna 

 (Thysanocrinus, Ichthyocrinus, Eucalyptocrinus etc.) 

 mentioned above. Stromatopora and, locally, the corals 

 Holy 'sites catenlatus {catenularia) and Favosites favosus 

 are characteristic. At Shelby the 32 feet of Lockport 

 dolomite separating the Guelph faunas are free from 

 Guelph fossils. 



The Guelph dolomite (Bell '63) receives its name from 

 Guelph in Canada. In New York it is a thin-bedded, 

 black or steel gray dolomite that gives off a strong odor 

 of petroleum when freshly fractured. About 15 feet 

 seems to be the maximum thickness. The double occur- 

 rence at Shelby, Orleans county, has been mentioned 

 above under the discussion of the Lockport group. The 

 lower occurrence, the Lower Shelby dolomite, contains 

 the purer Guelph fauna; the Upper Shelby dolomite has 

 Lockport species included in its fauna. Farther west the 

 Guelph part of the Lockport group appears only at the 

 top, with a thickness of 140 feet in Canada. This for- 

 mation is known as far east as Wayne county. A total 

 of over 70 species are now known for the Guelph of New 

 York and of these 17 also occur in the dolomite below. 

 The Guelph dolomites are the last true marine deposits 

 of Silurian time in New York. The Lockport sea was 

 shallowing and gradually becoming more inclosed, with 

 an accompanying increase in salinity and magnesian con- 

 tent of the sea water. Coral reefs became very abun- 



