226 TWENTIETH REPORT ON THE STATE CABINET. 



LIST or THE SPECIES OF AMERICAN GRAPTOLITES HAVING A SINGLE 

 SERIES OF CELLULES ON ONE SIDE OF THE STIPES OR BRANCHES, 

 INDICATING THEIR RELATION TO THE POINT OF ORIGIN OR INITIAL 

 POINT, SO FAR AS KNOWN. 



Genus G-raptolithus, Linnaeus. 



A. Species known only as simple and single stipes. (M onogi'aptus .) 



G. clintoni. 



B. Species having a bilateral arrangement of parts. (Sub-genus Monoprion, 



Barrande; Monograptus, Didymograptus, M'Coy.) 



a. Polypary consisting of two stipes from a single initial point, with 



the cellules on the upper or inner side. {Didymograptus, M'CoY, 

 in part; Cladograptus, Q^einitz, in part. 



G. arcuatus, extenuatus, pennatulusj 



bifidus, Jlaccidus, serratulus, 



constrictus, indentus, similis, 



divaricatus, nitidus, tenuis, 

 extensus, 



b. Polypary consisting of four simple stipes from a single axis, with or 



without a central disc. {Tetragraptus, Salter; DichograpUis^ 

 Salter, in part.) 



G.alatus (disc), crucifer (disc), headi (disc), 



bigsbyi, denticulatus, quadribrachiatus. 



bryonoidcs, fruticosus, " 



c. Polypary consisting of eight simple stipes proceeding from a single axis, 



with or without a central disc. {Dichograptus, Salter, in part.) 



G. octobrachiatus (Ahc) , odonarius. 



d. Polypary consisting of more than eight simple stipes proceeding from 



a single axis, with a distinct broad corneous disc. {Bichograptus, 

 Salter, in part; Loganogra'ptus, Hall). 



G. logani, logani, var. 



e. Polypary with the stipes proceeding from a single axis, and more or 



less frequently branched during their entire length ; not known to 

 have a central disc. 



G. abnormis, multifasciatus, richardsoni, 



flexilis, ramulus, rigidus. 



milesif 



f. Polypary developed from an initial point in two or more directions ; 



these divisions developing celluliferous branches, and themselves 

 becoming celluliferons towards their extremities {Cladograptus, 

 Carruthers; Ccenograptus , Hall). 

 G. gracilis, divergens, surcularis. 



