W. W. Dodge — Lower Silurian Graptolites. 153 



Art. XVII. — Some Lower Silurian Graptolites from 

 Northern Maine ; by W. W. Dodge. 



Eight years ago I pointed out a newly found graptolite lo- 

 cality in Penobscot County, Maine,* about seventy-five miles 

 north of Bangor and twelve east of Mt. Katahdin. I have 

 since obtained a few additional specimens there, and now re- 

 port them for the evidence they give as to the age of the 

 rocks in which they occur. 



The entire list of determinable forms before me is as fol- 

 lows : 



1. Helico c/r apt us gracilis Hall (sp.) 



2. Dicellograptus ? 



3. Diplograptus, n. sp. 



4. Cryptograptus marcidus Hall (sp.) 



5. Glossograptus spimdosus Hall (sp.) 



6. Young graptolite. 



This is clearly a fraction of the Norman's Kill assemblage 

 of species. 



No. 1 is represented by a single specimen, incomplete but 

 distinct and snowing well the 'peculiar proximal bar.' It was 

 taken from an extensive ledge that lies along the south bank 

 of the Wassatiquoik, about a mile above the junction of that 

 stream with the east branch of the Penobscot. Thin layers of 

 graptolite-holding shale are separated by considerable thick- 

 nesses of highly siliceous slate that varies in color from olive- 

 gray to deep blue-black. 



The specimens of No. 2 are too obscure for certain recog- 

 nition even of the genus. The hydrothecse are undistinguishable. 

 The branches have the double curvature that in different de- 

 grees is shown in several species of Dicellograptus, but they 

 do not include an angle agreeing exactly with that assigned to 

 any of the described species. 



The best specimen of Diplograptus yet obtained was found 

 in 1881 north of the stream, in a free, angular piece of shale, 

 and was then mentioned as D. pristis. It differs in some 

 particulars from D. pristis His., as described by Tullberg.f 



The free portion of the outer margin of its hydrothecse is 

 unusually long, equalling three-quarters of the width of the 

 polypary, (lf mm : 2f mm ). The specimen has fewer hydrothecse 

 in a given length of polypary than any described species, X 



*This Journal, Dec, 1881, vol. xxii, p. 434. 



f Bihang till Kongl. Svenska Vetenskaps-Akademiens Handlingar, Bd. vi, No. 

 13, pp. 10, 11, taf. 1. 



X D- peosta excepted, if necessary ; description of which I have not been able 

 to consult. For the name, see Wisconsiu Geological Report 1862, p. 430. 



