Rules and llisruJes in Classification. — 3farcon. Ill 
Fig. 18. Natural cast, from the Orthoceras bed. Ventral valve with 
the exterior profile restored in broken line. 
Pig. 28. Cast taken from a natural cast of a dorsal valve, Orthoceras 
bed. 
Numbers 14 to 17 are from near Spring Valley, numbers 18 and 28 
from near Granger, Minnesota. 
Orthis porrecta n. sp., figs. 19 to 24. 
Pig. 19. Ventral view of specimen with shell, Triplecia bed. 
Pig. 20. Ventral plication of last analyzed. 
Fig. 21. Lateral profile. 
Fig. 22. Longitudinal median section. 
Pig, 23. Interior of dorsal valve. 
Fig. 24. Cast taken from interior of a ventral valve. 
All are from near Wykoff, Minnesota. 
Orthis futilis n. sp., fig 25 to 27. 
Fig. 25. Ventral view of full sized specimen, Triplecia bed. 
Pig. 26. Profile of the same, partly reconstructed. 
Fig. 27. Ventral plication of the same X 2. 
Prom near Granger, Minnesota. 
Fig. 29. Diagram showing the gradual change in the median fasci- 
cle of plications, from single ventral median plication with paired off- 
sets (a), to altei-nating offsets (6), to nearly paired (c), and paired (d) me- 
dian and first ofl'set plications. 
RULES AND MISRULES IN STRATIGRAPH IC 
CLASSIFICATION. 
By Jules Maecou, Cambridge, Mass. 
CONTENTS. 
Page. 
Swaiiton and Quebec City formation Ill 
The Stockbridge limestone at Kutland 113 
Tlie Green Mountains in Massachusetts 114 
Tiio New Red, or Dyas and Trias 116 
•Jura Hi) 
The Laramee formation and tlie Puerco beds 120 
Tiie Chico-Tejon formation 121 
Quaternary or Pleistocene 12.5 
Conclusions 12ft 
Post-Scriptum— New Geological map of New York 126 
The Swanton and Quebec-City Formation. 
At Swanton, (Vermont) and at Quebec city, we have about 
live thousand feet of strata, almost all slates, with a few len- 
ticular masses of limestone, in concordance of stratification 
with the Phillipsburgh and Pointe-Levis group, and which 
contain a fauna of graptolites, with now and then, in sporadic 
geographic distribution, a few fossil forms which develop as 
