1852.] LOGAN POTSDAM SANDSTONE FOOT-PRINTS. 205 



stone for lime-burning, and it has been much quarried at the village 

 of St. Genevieve, just opposite the mid-length of Isle Bizard. The 

 White Horse Rapids are situated about three miles to the east, and 

 here, on both sides of the Riviere des Prairies (a branch of the 

 Ottawa), black limestone-beds, lying in the form of a shallow trough, 

 and displajdng fifteen species of Trenton and one of Chazy fossils, are 

 surmounted by "black bituminous shales holding Triarthrus Beckii 

 and Graptolithus bico?mis of the Utica Slate, while loose fragments 

 of black hmestone (possibly Trenton limestone) at no great distance 

 are characterized hj Leperditia gracilis (Jones, MS.) and. Serpulites. 

 The Trenton Limestone of this part is probably continuous with that 

 of the south side of Montreal Island, where, about three miles W. of 

 Lachine, on the road to St. Ann, fifteen Trenton species have been met 

 with ; and in the quarries of Point St. Claire, six miles nearer St. 

 Ann, we get five species characterizing the Bird's-eye Limestone, with 

 one usually found in the Chazy, and four given by Hall to the Trenton. 



Point St. Claire^, 



Favistella (Columnaria) alveolata Trenton. 



Stictopora acuta 



Leptaena sericea 



alternata 



Pleurotomaria umbilicata Bird*s-eye. 



Murchisonia perangulata 



Modiolopsis obtusa 



Favosites alveolaris? 



Phytopsis cellulosa 



Atrypa plena? Chazy. 



Three Miles above Lachine. 



Favosites (Chaetetes) lycoperdon , Trenton. 



Orbicula lamellosa 



terminalis? 



Leptaena sericea 



deltoidea; plentiful 



Orthis (testudinaria) striatula (Emmons) 



pectinella 



Modiola (Tellinomya) anatiformis? 



Bellerophon bilobatus 



Oncoceras constrictum 



Cyrtolites trentonensis 



ornatus 



Calymene senaria; plentiful 



Isotelus gigas 



Leperditia (L. Canadensis ?), a species -^ inch long. 



Orthoceras. 



Serpulites, allied to S. dispar (Salter). 



Conularia. 



Encrinums, the same as at White Horse Rapids. 



White Horse Rapids. 



Favosites (Chaetetes) lycoperdon Trenton. 



Stictopora acuta ,, 



* These lists, and the names of the other fossils mentioned in the paper, are 

 furnished by my friend Mr. Salter, of the Geological Survey of Great Britain. 

 VOL. VIII. PART I. P 



