NOKTll AMERICAN PALAEONTOLOGY. 285 



Williams, Henry S. Devouian Lamellibraucbiata aud Species-mak- 

 ing-. (Amer. Jour. Sci., 3d ser., vol. xxxii, pp. 192-198, September, 

 1886. New Naven.) 



A criticism of ''Palfeontology, vol. V, part i, Lamellibranchiata II, text and 

 plates. Contaiuiug descriptious aud figures of the Dimyaria of the Upper 

 Helderberg, Haiuiltou, Portage, aud Chemung groups, by James Hall, State 

 Geologist, Albany, New York, 1885. 



Williams, Henry^ S. Devonian Lamellibranchiata and Species-mak- 

 ing. (Nature, vol. xxxiv, p. 539, 1886. London and New York.) 

 Notice of. See American Journal of Science, September. 



Williams, Henry^ S. On the Classification of tlie Upper Devonian. 

 Proc. A. A. A. S., vol. xxxiv, part i, pp. 222-234, 1886. Salem.) 



Concludes: (1) That the Devonian black shales carry a fauna (B) which re- 

 a2)pears with slight moditication wherever the black shales appear, from 

 the Genesee shales up through the Portage deposits to the Cleveland shale, 

 and possibly higher. These deposits run out aud disappear at the eastern 

 extreme of the area. (2) The Portage rocks and their fauna (C) are com- 

 paratively local, belonging to the central part of the area, the fauna failing 

 in the more western sections, aud both fauna aud lithologic characteristics 

 are unrecognizable east of the Cayuga section. (3) It is evident from the 

 study of the sections that the interval occupied in the Genesee section by 

 the typical Portage fauna is represented in the Cayuga section by an en- 

 tirely diftereut set of species (the several stages of A), while still farther 

 east in the Chenango and Uuadilla section the same interval is filled by a 

 preliminary stage of the Catskill (F. 1), (4) The Ithaca group of the State 

 reports contains faunas (A., 3, 4) which he has defined as stages in the suc- 

 cessive modifications of the Hamilton fauna. This set of faunas ditfers from 

 the Chemung fauua in the absence of several of its common and abundant 

 species, and by presenting unmistakable evidences of earlier stages in modifi- 

 cation of species which are near enough alike to be classified under the same 

 specific name. (5) The series of modified stages of the Hamilton fauna (A., 

 1-7) is confined to the sections east of theCanandaigua meridian. The lowest 

 stage (A. 1) occurs at the extreme east, where the Tuliy limestone and the 

 black Genesee shale are scarcely to be recoguized. The third and fourth stages 

 do not appear at the extreme east, but only in the Cayuga aud Tiaughuioga 

 sections, their place farther east being occupied by the first stage of the 

 Catskill. The following stages appear in the more eastern and fail iu the 

 Cayuga section, while the final stage (A. 6 and A. 7) extends farther west, 

 aud appears after the Chemung species have appeared in the deposits of the 

 region. (G) The Catskill deposits of Chenango and Otsego Counties are in- 

 trinsically not distinguishable from the ui^per stage of the Catskill, but 

 appear at a lower jjosition stratigraphically in the interval occupied by 

 the " Ithaca group" of the Cayuga section and by the middle part of the 

 Portage group of the Genesee section ; but palsentologically they are im- 

 mediately ])rece<ied by stages of the Hamilton fauna, aud are followed by 

 later stages of the same general fauua. (7) The Chemung fauna appears, 

 in what I consider its earliest biological stage, in the central sections (D. 

 and D. 1), but the predominant aud most characteristic species of the Che- 

 mung appear stratigraphically earliest in the more western sections (D. 4 of 

 Girard and Chatauqua). This stage of the fauna appears iu the upper jjart 

 of the Chemung group of the more eastern sections, and when we reach the 

 more eastern part of the area (the Chenango and Uuadilla sections) this 



