168 



allowance of a few inches of strata, which may be styled passage-beds 

 or beds of transition, constitute the lowest portion of the Utica forma- 

 tion, as it is developed at Rideau, where it overlies, perfectly conforma- 

 bly, the black, nodular and impure bituminous limestones of the 

 Trenton formation, which begins immediately below these sections, 

 and wliich at the northern end of Crichton street are clearly observed 

 as thick bedded limestones, characterised by the presence of Murchisonia 

 hellicincta, Hal), StropJiomena alternata, Conrad, Leptcena sericea, 

 Sowerby, monticuliporoid corals, (probably Prasopora Selwyni, Nichol- 

 son), etc., all eminently Trenton in fades. 



From these beds of the Utica formation in Eideau the following 

 species of fossils v;ere obtained during the summer of 1887, which 

 illustrate the palaeontology of the rocks in question and indicate the 

 fauna which swarmed in the old Ordovician or Cambro-Silurian sea 

 about Ottawa. 



I. Rhabdophora : 



1. Leptograptus flaccidus, Hall. 



L'. Orthograptus quadribrachiatus, Hall.t 



3. 1 1 Sagenella ambigua, Walcott. 



II. POLYZOA : 



4. Helopora sp.'' 



5. Batostoma erraticum, Ulrich. 



III. Brachiopoda : 



6. Lingula obtusa, Hall. 



7. " Cobourgensis, Billings. 



8. " Daphne, Billings. 



9. Leptobolus insignis. Hall. 



10. Lepttyna sericea, Sowerby. 



11. Strophomena alternata, Conrad. 



12. Orthis bella-rugosa, Hall. 

 12. " testudinaria, Dal man. 



14, '' emacerata, Meek. 



15. " sp (cf. O. pectinella, Conrad.) 

 IG. Zygospira Headi, Billings. 



