62 BULLETIN 65, UNITED STATES NATIONAL MUSEUM. 



Genus THAMNOGRAPTUS HaU. 



Thamnograptus Hall, Rop. Progr. Geol. Surv. Canada for 1857, 1858, p. 143, 

 nomen nudum; Nat. Hist. New York, Pal., Ill, 1859, 1861, p. 519; 1.3th 

 Rep. New York State Cab. Nat. Hist., 1860, p. 62; Can. Org. Rem., 

 Decade 2, 1865, p. 141; 20tli Rep. New York State Cab. Nat. Hist, 1S6S, 

 p. 218 (rev. ed., 1868 [1870], p. 251).— Nicholson, Mon. Brit. Graptoli- 

 tidiK, 1872, p. 130: Ann. and -Mag. Nat. Hist. (4), XVI, 1S75, p. 270.— 

 Zittel, Haudbiicli d. Pal., I, 1S79, p. 290. — Spencer, Trans. Acad. Sci. 

 St. Louis, IV, 1SS4, pp. 563, 589; Bull. Miis. Univ. State Missouri, I, 

 1884, p. 39.— Miller, North Amer, Geol. and Pal., 1889, p. 207.— Pocta, 

 Syst. Sil. Centre Boheme, ^'III, Pt. 1, 1894, p. 165.— Elles and Wood. 

 Mon. Brit. Graptolites, Pal. Soc, 1903, p. xli. — Ruedemann, New York 

 State Mus., Mem. 11, 1908, p. 204. 



This peculiar genus was founded upon two Ordovician species of 

 grajitolites, which have recently been studied by Ruedemann. The 

 ab.sence of theca; or apertures upon the branches has always kept the 

 genus doubtful, and the following descriptions of the Niagaran forms 

 can not be said to add anything to the knowledge of the genus. 



The original diagnosis is: 



Bodies consisting of straight or flexnous stipes (siniiile or conjoined at base?) 

 with alternating and widely diverging branches; branches long, simple or 

 ramose, in the same manner as the stipe. Substance fibrous or striate; the 

 main stipe and branches marked by a longitudinal central depressed line, in- 

 dicating the axis. Cellules or serratures unknown.' 



Genotype. — Tliamnograptus typus Hall (^= Thamnograptus eapil- 

 laris Emmons). Xornianskill shale, Kenwood, near Albany, New 

 York. 



THAMNOGRAPTUS BARTONENSIS Spencer. 



Thamnoonipfius harlonensis Spencer, Canadian Nat, VIII, 1878, pp. 4."^. -162. 



Thamnograptus bartonensis Spencer, Trans. Acad. Sci. St. Louis, IV, 

 1884, pp. 565, 589, 590, pi. 6, figs. 4, 5: Bull., Mus. Univ. State Miss(»uri, 

 I, 1884, pp. 15, 39, 40, pi. 6, figs. 4; 5.— Gurley, Jonru. (icol.. IV, 1S9li, 

 pp. 101, 309. 



The original description follows : 



Stipes single and broad with lineal undulating branches alternately arranged 

 on opposite sides and having half the thickness of the stii)e, which is as much 

 as one-sixteenth of an inch broad. The branches which are given off are 

 usually at right angles with the stipe; and are generally half an inch apart; 

 there being an undulation of considerable length opposite to their place of 

 attachment. 



Texture corneous and black, the surface being nearly smooth with longi- 

 tudinal depressions. The branches are usually short and abrui)t. 



They occur in the Niagara Ijimestone at Hamilt(m, Ontario, and the writer 

 has seen them in the rock several inches long. 



Quoting from Doctor Gurley's manuscript : 



The description of 1884 adds: Branches having half the thickness of the 

 stipe, their bases nearly at right angles with it, but afterwards they bend ui)- 



