156 Cincinnati Society of Natural History. 



Genus i. — Graptolithus, Linn, 1768. 



Polypary simple, linear, commencing with a more or less 

 attenuated, generally curved base, and possessing only a 

 single row of cellules on one side ; the cellules generally 

 overlap to a greater or less extent, and are never separated 

 by non-polypiferous portions of common canal. (Emend, 

 Nicholson, Mon. Brit. Grap., 1872, p. loi, as Graptolitcs). 



RtDiarks. — Nicholson notes that the above definition does 

 not correspond to the original one of Linnseus, nor to the 

 later definition of Hall. It is made to include, however, those 

 forms that in an adult condition have only a single row of 

 cellules on one side. The two species commonly referred to 

 this genus from the Cincinnati group are G. gracilis and G. 

 subtenuis. As regards the genus itself Dr. Gurley says : 



" Graptolithus has practically been abandoned ; because, 

 first, it was established for, and as at first defined included, 

 only inorganic objects {Dendrites, etc.), and second, it has 

 been used for everything until it now means nothing. When 

 used at all by the latest writers, it is in the sense of the ex- 

 clusively Upper Silurian Monograptusy 



In regard to the form identified as G. gracilis, from Cincin- 

 nati, Dr. Gurley says.: " So far as can be determined from 

 the material I have seen, the specimens identified as Grapto- 

 lithus gracilis, Hall, and Dcncirograptus gracillinnini, Lesqx., 

 seem much alike. I judge, how^ever, from single specimens 

 of each, and these leave much to be desired. The only 

 criteria are the thickness and general aspect of the branches, 

 which seem much the same. This gracilis bears no relation 

 to Stepha)iograptus gracilis, from Norman's Kill, New York, 

 which is the only ' Graptolithus gracilis' Hall described. 

 Better specimens might show different features, h\\\. jirobably 

 that called G. gracilis is Dendrograptus gracilliniuni, Lesqx. 

 Dendrograptus gracilis. Hall, is, I think, Cnlciferous, which is 

 strong presumptive evidence against the reference of the Cin- 

 cinnati form to that .species." 



In regard to G. subtenuis. Hall, and G. tenuis, Portlock, Dr. 

 Gurley writes: " Portlock's species is Monograptiis tenuis of 

 the Upper Silurian. To it has been referred almost every 

 species which was slender and had the theca> confined to one 

 side. The American species that has been referred to it is 



