Expl w ltioh <ik Plates. 

 PLATE 12. 



Pionai l—Strophodonta mueronata, Conrad, var. Tally limestone; Cuyler, N. Y. Ventral valve 



natural - 

 I h.i ai - -'. 3, I— The same: enlargement of the surface markings, Bhofl ing the mode of bifurcation 



and intercalation of the plications on specimens similar in other respects from a single 



locality. Figure '1 is enlarged about three diameters, and figures :i and 4 about ten diameters. 

 Fiot bes 5, 6, IShynchoneUa pugnus, .Martin, var. called fi. aita. Calvin. Solon, Iowa. Natural size. 

 Piot ass 8,9— Productus hallianus, U'alcott (-- Productus dissimiUs, Hall). Ithaca formation, Ithaca, 



N. V. Ventral (8) ami dorsal (9) valves, natural size. 

 Fioubi 10— Chonetei logani, var. aurora, Hall. Tally limestone. Ordinary size and form. 

 Fi'.i BE 11— The same. Enlarged nearly four diamet-rs. 

 Fionas 12— Spirifer mueronatus, Hall, var. tullu nsis, II. S. W. Tully limestone. Tinker's Palls, N. Y- 



Exfoliated specimen of dorsal valve representing the common form of the Tully variety. 

 PlOl iik IZ— Spirifer mueronatus, Hall, var. Hamilton formation. Chenango, N. Y. This Bpedmen 



represents one of the later Hamilton mutations of the species, and figure 12 represents the 



stage of mutation intermediate between figure 13 aud Spirifer nusacostalis of the Ithaca 



fauna. 

 Fioi Bis U. 16 Platyceras tymmetricum, Hall, var. Tully limestone; Truxton, N. Y. 

 FlOUBI 16— Orthis tuUiensis, Vanuxem. Tully limestone; Tinker's Falls, N. Y. Exterior view of 



dorsal valve of specimen larger than average size. 



PLATE 13. 



Copit iiin! tiqiires of Khynchonella cuboides, Sow., etc., an ■ of specimens of R. venns- 



tula, Hull, / d, the geographical modifications of the form first notit the 



name Atrypa cuboides, Sow. (I8ln). From England, Germany, Russia, China, and .V km. 



Fiocbes 1, 5— Atrypa cuboides, Sowerby ; South Devonshire. Trans. Geol. Soc, 2d Ser., Vol. V, PI. 



I.VI, Bg. 24. 

 K i • . i i.)- '//>'! itnpleta, Sowerby; South Devonshire. Trans. Geol. Soc, 2d Ser., Vol. \', IM- 



I.VI I, fig 

 Piovku 1, 19— Bhynehonella procuboides, Kayser; Eifel. Zeitschr. d deutseh. geol. gesell., Bd. 



Will, Taf. IX, tigs. 3a, 36. 

 ].-,,,, ,.,. g_ Terebratula Sowerby), Phillips; South Devonshire. Figs, and Descr. Paloaozoic 



Mils, etc, PI. XXXIV. Bg. 160. 

 i-'i-.i i.i - 3, 0, 16, 30— Terebratula < - rerby), Geinits; Saxony. Die Versteinerungen der 



Grauwacken-formatlon, Beft LI, Taf. 14, figs. 28, 20. 



l- ;i- i,-, 14,23,24,27,20,31,32, 33, 84— EhynchoneUa venustula, Sail; Tully limesl , Tinker's 



La, etc., New fork. Original drawings. 

 Fiqubh 10, 11, 12, 16, 17, 18, 10, 21, 22, 26, 28— Rhynchom . Sowerby; according to sundry 



authors, u^ follows : 



Fioubh 10, 21— Koltaban, 1 Russia; Techernyschew. Mem. du ComiU geologlque, Vol. 1, No. 8, 



FioubbsU, 16 Dewltsa, | Taf. Ill, figs. 10a, 106, 11a, 116. 



Fi..i bi - 18,2! /.•■rin. Russia; Tsohernysohew. Mem. du Com i to U'oiogique, Vol. Ill, No. '■'■, Taf, 



XIV, tigs. \e, id. 



Fioubbs 12, 17— Woronesch, Russia; WenjukofT. Die Fauna der Devonischen systems Im Nord* 



tlichen I Centrales Russian I, 1888, Taf. V, figs. lOo, 106. 



Fiodbbs 19, 26— Ohlna, Kayser. Von Rlchthofens' China, Vol. IV. Taf. VIII, tigs. 2s, 2<i. 



>— Grand, Germany, original drawing. 







