DENDROID GRAPTOLITES OF HAMILTON, ONTARIO. 



57 



The best preserved graptolites tbat are found at Hamilton occur on the shaly 

 surface of the limestone, but this species is only found in the highly crystalline 

 rock, and consequently, although the general form of frond is well preserved 

 and very beautiful, the detailed structure is not shown as well as in the forms 

 that are found in the more perishable shaly rocks. 



Gurley adds the following: 



This species is easily recognizable among the now known Acanthograptiis 

 species by the very heavy branches, which very generally measure 1 mm. or a 

 little more, though occasionally one as narrow as 0.8 mm. is seen. As regards 



Figs. 



rS, 74. ACANTHOGRAPTUS GRANTI SpENCER. 73, DlSTAL PORTION OF EHABDO- 



soMEj X 5; 74, A nearly perfect rhabdosome. (After Ruedemann.) 



number, they are set rather irregularly, but usually there are about 15 in 

 L!5 mm. of width. The specimens show no evidence of thecse or of a virgula. 



Plesiotypcs. — Cat. No. 55310, U.S.N.M. Sj)ecimen figured on Plate 

 2, figure 1, in Spencer collection. 



ACANTHOGRAPTUS WALKERI (Spencer). 



Inocaulis u-(tlkeri Spencer, Canadian Nat., X, 1882, p. 165, nomcn nudum; 



Trans. Acad. Sci. St. Louis, IV, 1884, pp. 504, 585, 586, pi. 5, fig. 2; 



Bull. Mus. Univ. State Missouri, I, 1884, pp. 14, .35, 36, pi. 5, fig. 2.— 



Gurley, Journ. Geol., lY, 1896, pp. 99, 309. 

 Acanthograptiis walkeri Ruedemann, New York State Mus., Mem. 11, 190S, 



p. 194, pi. 6, flgs. 1, 2 ; pi. 7, fig. 4, text flgs., 97, 98. 



