THE GUELPH FOEMA.TION OE CANADA. 551 



in that genus. The species is distinguished by its short but elevated 

 spire, its large body-whorl, becoming almost disjunct at the aper- 



Fig. Holopea occiclentalis, Nich. 



ture, its circular aperture, and large umbilicus. The upper whorls 

 are almost uniformly convex ; but the body-whorl is obtusely an- 

 gulated at about its upper fourth, being somewhat flat from this point 

 to the suture. The suture is deep. There are no traces of a band 

 or carina. 



Formation and Locality. Guelph Limestones ; Elora, Ontario. 



EXPLANATION OF PLATE XXVI. 



Fig. 1. Murchisonia Boylei, Mch., of the natural size. 



2. Murchisonia Hercynia, Billings, nat. size. 



3. Fragment of large specimen of Murchisonia Loganii, Hall, of the natural 



size. 



4. Longitudinal section of another example of the same, showing the form 



of the columella ; nat. size. 



5. A small example of Subuliies ventricosus, Hall, nat. size. 



6. A large, but imperfect example of Murchisonia Vitellia, Billings, nat. 



size. 



7. Murchisonia bivittata, Hall : two whorls exhibiting the form of the colu- 



mella, of the natural size. 



8. A small example (cast) probably referable to Murchisonia bivittata ; nat. 



size. 



9. A large but imperfect example of Murchisonia macrospira, Hall (?), partly 



showing the interior ; nat. size. 



10. Fragment of Murchisonia turritiformis, Hall ; nat. size. 



11. Fragment of the cast of Murchisonia longispira, Hall; nat. size. 



12. Longitudinal section of another example of the same, showing the form 



of the columella ; nat. size. 



13. 14. An undetermined species of JPleurotomaria, nat. size. 



15. Under surface of Pleurotomaria solarioides, Hall, nat. size. 



16. 16a. CycIonema(?) elevata, Hall, nat. size. 



17. Cast of Holojpea Gfracia, Billings, nat. size. 



18. Cast of Holopea guelphensis, Billings, distorted by pressure ; nat. size. 



