220 J. W. Judd — On the use of the term Neoeomian. 



Appendix.— 1. "We are enabled, thanks to Principal Dawson, to 

 offer a good drawing (PI. IX., Fig. 15) of a specimen of the Nova- 

 Scotian Estheria, roughly figured in a woodcut at p. 256 of "Acadian 

 Geology," 1868. Not being well preserved, this specimen shows 

 no reticulate or other ornament besides the concentric ridges. These 

 are bold and distant, as in E. PortlocTci, E. Mangaliensis, &c. ; but as 

 the form before us differs in outline from the broad-ridged species, 

 we may regard it as distinct, and catalogue it as E. Dawsoni. It 

 occurs in the Lower Carboniferous rocks at Horton. 



2. Another species of Estheria has lately come into my hands, 

 through the kindness of Mr. C. Peach. Several specimens have been 

 found in argillaceous concretions in the Carboniferous Shales of 

 the Camstone quarry, at Salisbury Craigs, Edinburgh, by Mr. B. N. 

 Peach. It is a subquadrate form, boldly ridged. Its sculpture is not 

 preserved, and, indeed, only mere films of the shell itself. The form, 

 however, is sufficiently distinct to authorize us to regard it as a new 

 species — E. Peacliii. 



EXPLANATION OF PLATE IX. 



Fio. 1. Estheria Adamsii, sp. nov. a, Left valve shown ; natural size, b and e. 

 Ornament (c, near the margin) ; magnified 40 diameters, 



2. Estheria Adamsii, (?). Right valve shown ; 2 diam. 



3. Anthracomya PMllipsii, "Williamson, sp. Nat. size. 



4. Carhonia Evelines, sp. nov. a. Left valve shown; magn. 25 diam. b, 



Muscle-spot ; 70 diam. c. Dorsal view of the two valves ; 25 diam, 



6. Carhonia ? sp. A cast ; 25 diam. 



6 & 7. Carhonia Agnes, sp. nov. 6«, Left valve shown; 25 diam. 63, Ee- 

 ticulation on the cast, and 6c, the mnscle-spot; 70 diam. Fig. 7. Dorsal 

 edge of the left valve, and outline of the other ; 25 diam. 



8 & 9. Carhonia Agnes, var. rugulosa, nov. 8. Left valve shown ; 25 diam., 

 9. Muscle-spot and reticulation of the cast ; 70 diam. 

 10. Carhonia Agnes, var. subrugiclosa, nov. Left valve shown ; 25 diam. 

 11-14. Leaia Leidyi, Jones. Various forms : differences due to age, sex, or 

 variety, probably the first. Fig. 11a, Left valve, old; 5 diam. 115 and 

 c. Ornament {c, near the margin) ; 40 diam. Fig. 12, Left valve, adult 

 (typical form) ; 5 diam. Figs. 13 and 14, Young right valves; 5 diam. 



15. Estheria Baivsoni, sp. nov. Left valve (cast) ; 5 diam, 



16. Estheria tenella, Jones. Eight valve ; 5 diam. 



17. Estheria Peachii, s^. nov. Eight valve; 5 diam. 



IS. Anthracomya (young of A. Phillipsii? See fig. 3.). Magn. 10 diam. 



VII, — On the Use of the Term Neocomian. 

 By John W. Judd, F.G.S., of the Geological Survey of England and "Wales. 



THE confusion which has of late years resulted from the multipli- 

 cation of names for the same geological stratum, formation, or 

 system, sufficiently indicates the necessity for the adoption of certain 

 rules by which our geological nomenclature may be reformed and 

 brought into a state of something like uniformity. When this 

 necessity is acknowledged, but little doubt can arise as to the 

 principles on which such rules must be based ; the law of priority, 

 with certain necessary limitations and exceptions, will be made to 

 govern the terminology of Geology, as it already does that of almost 

 every other Natural Science. The nature and mode of application 



