236 TWENTIETH REPORT ON THE STATE CABINET. 



and, as now appears, with as mucli reason for its adoption as the term 

 Didymograptus^ which cannot properly be so extended as to include all the 

 species originally named under it. 



I have little doubt that the forms to which Mr. Carruthers has 

 applied the name Cladograptus are similar to our G. gracilis and G. diver- 

 gens, to which I have applied the name Ccenograptus ; and it may be a 

 question whether the Nemagraptus of Emmons, proposed in 1855, is not 

 of the same character ; though the remarks of that author concerning the 

 cellules would, if verified, exclude the typical species from that group. 



The discussion in regard to nomenclature is at this time of small 

 consequence, compared with that of the structure; and, on this account, 

 these forms require to be separated from GtRAPTOLITHus proper. 



The question as to the limitation of the term Graytolithus still remains 

 a matter for discussion. I have, on page 170, repeated what I had previ- 

 ously written upon this subject, and I still find little reason for a modifi- 

 cation of those views. Mr. Carruthers, speaking of the compound 

 forms so common in our rocks, remarks : " Whether or not all the 

 " American graptolites are fragments of this more complex form, I cannot 

 "say; but it is certain that few if any of the European species could 

 " belong to it. In many species the termination of both the extremities 

 "of the polypary is known, and that end which should be united to the 

 " compound group is certainly free." This might have been said of our 

 own species in past time ; but experience has proved it otherwise, and at 

 this time we have but one form of the monoprionidian type which we suspect 

 to have grown in single stipes. But if this be true of European species, 

 they have been erroneously represented. Even taking Mr. Carruthers' 

 own figures of "two perfect specimens of G. clingani,'''' we are scarcely 

 willing to accept the assertion. If we examine all the figures of 

 PoRTLOCK, we shall find that no one of them gives evidence of complete- 

 ness at the base ; and including the figures of Salter, Harkness and 

 M'CoY, we shall find no better evidence of it. Consider also Mr. 

 Carruthers' description of Cladograptus, where he says "the polypi- 

 "dom, at its origin near the base, is very narrow, being little more than a 

 "fine line: as it increases in length, it increases in breadth," &c. Now 

 had this been broken off, when filled with the common body, where it had 

 the width of a fine line, would it not have become less from consequent 

 contraction, and have appeared as if complete at its lower extremity ? When 

 we look at such forms as G. gracilis in the slender attachment of the stipes 

 to the common rachis, could we decide, in their separated condition, whether 

 they were entire bodies, or stolons from a common body ? I do not mean, 

 however, to assert that there are no single monoprionidian stipes which 

 are complete in themselves. 



I am willing to reassert here what I have before said, that in the sepa- 

 rated portions of the Grraptolites we cannot distinguish between Didymo- 

 graptus, Tetragraptus and Dichograptus ; and in regard to the latter 

 term, if it is to be brought into use, we have a right to some explanation 



