PLATE 54. 



Fig. 1. HOLOPEA SUBCONICA. 294 



1 a. View showing the aperture, which is represented with peristome too much thickened. 



1 6. The anterior side of the same. 



Pig. 2 & 3. HoLOPEA ANTIQUA. 294 



2 a. A cast of this species of the ordinary size. 



2 6. A similar cast, which is a little more ventricose. 

 8 a. A cast of a larger specimen. 



8 b. The anterior view of a larger individual. The apparent extension of the shell on the 

 lower side is a misrepresentation by the artist. 



Fig. 4 & 5. HoLOPEA ANTIQUA, var. pervetdsta. 295 



4. A cast of this species. 



5. A specimen retaining the shell. 



Fig. 6 & 7. HOLOPEA? ELONGATA. 295 



6. A section of a small individual shown on the worn surface of the rock. 



7. A larger specimen which preserves some remains of the columellar lip, the upper volutions 



being entire. 



Fig. 8. LOXONEMA ATTENUATA. 296 



8. The posteiior side of the cast, the aperture being filled with stone. 



Fig. 9 & 11. LoxONEMA PITCHI. 296 



9. Anterior side of a cast which is flattened in that direction. 

 11 a. A fragment of the same species from the shaly limestone. 

 11 6. A similar fragment of a larger individual. 



Fig. 10. LoXONEMA? OBTUSA. 297 



10. A longitudinal section of a specimen of this species upon the worn surface of the rock. 



Fig. 12. LOXONEMA? COMPACTA. 297 



12. A specimen from which the shell is exfoliated, preserving thirteen volutions with the apex 



imperfect. 



Fig. 13. LoXONEMA PLANOQYRATA. 298 



13. The anterior side of the specimen, the apex of which, as represented in the figure, preserves 



no marks of volutions. 



Fig. 14. HOLOPEA DANAI. 295 



14. Anterior view of the cast of this species. 



Fig. 15 & 16. MuRCHisoNiA extenuata. 298 



15. Copied from a figure of Mr. Conrad, which is cited as from the Tentaculite limestone of 



Fayetteville, Onondaga county. 



16. A much worn specimen, which is perhaps of the same species. 



Fig. 17. MURCHISONIA MINUTA. 298 



17. Representations of the specimen, natural size and enlarged, from figures by Mr. Conrad. 



Fig. 18 a - e. Spiborbis laxus. 349 



18 a. A fragment of stone, preserving numerous individuals of this species. 

 18 b. The upper side of the spire of a specimen, gieatly enlarged. 

 18 c. The lower side, showing the round mouth and the umbilicus. 

 18 d. A specimen in which the last volution is free (a common condition of the species). 

 18 e. A specimen in which the apex is closely involved, and the remaining portions not con- 

 tiguous. ( This is an extreme form, and rarely seen.) 



