10? The Middle Devoxiax Deposits of Maryland 



l^reparod a table giving the 12 species occurring most frecjuently in it in 

 eastern Now York, anotlier from the lists of Dr. Cleland giving the 14 

 most frequent species in the Cayuga Lake region, and a third from the 

 lists of Grabau giving the 12 most frequent species from Eighteen Mile 

 Creek in western New York. From these three tables another one 

 was compiled by Williams Avhicli he called the " Tropidoleptus fauna: 

 Standard list of dominant species for the New York-Ontario province." 

 He furthermore stated that it was concluded on balancing up the various 

 kinds of evidence that this list " contains the 12 most characteristic 

 species of this fauna as it appears in the New York province, and shows 

 the order of ajiproximate rank they occupy in the faima as a whole." * 

 The 12 species composing this standard dominant list for New York is 

 as follows : 



1. Spirifer pennatus (^ mucronatus). 



2. Phacops rana. 



3. Tropidoleptus carinatus. 



4. Ambocoelia umbonata. 



5. Athyris spiriferoides. 

 (). Palaeoneilo constricta. 



7. Spirifer granulosus. 



8. Chonetes coronatus. 



9. Nuculltes triqueter. 



10. Nucula corbuliformis. 



11. Nuculites oblongatus. 



12. Nucula bellistrlata.- 



By reference to the ]\Iaiyland lists it will l^e found that every one of 

 the 12 species mentioned above as constituting the standard dominant 

 list of the New York Hamilton is found in the Hamilton beds of 

 Maryland. 



Furthermore. Williams ])repared another table by adding to the stand- 

 ard list the distributional value of all the species reported bv Prosser 

 in 37 faunules of the Unadilla region, that were not considered in the 

 standard list, which he called a " Revised list of dominant species of 

 the Hamilton formation of eastern New York and Pennsylvania, as 



* Loc. cit.. p. 61. 

 = Ibid., p. 60. 



