234 TWENTIETH REPORT ON THE STATE CABINET. 



SUPPLE3IENTAIIY NOTES. 



REMARKS UPON THE GENERA DIDYMOGBAFTUS (M'CoY) CLADOGRAPTUS 

 (Geinitz), CLADOORAPTU8 {Carrjjtwer'S,); DICRAN0GRAPTU8 AND ^CCEJVO- 

 GRARTUS iHAT.1.). 



In 1851, Prof. M'Coy (British Palaeozoic Fossils, page 9) suggested 

 tlie name Didy?nograptus in the following manner, after describing Biplo- 

 graptus ? sextans (Hall, sp.) : 



" From the strong affinity between this and the D. furcatus (Hall, sp.), 

 I provisionally leave it in the present genus, though it differs much from 

 the normally formed species. Those species, bifid from the base as this, 

 the serratulus (Hall), viurchisoni (Beck), &c., form a little group, having 

 one row of cells on each branch, sometimes on the inner and sometimes 

 on the outer edge : if necessary, these might be called Didymograptus — 

 the twin graptolites." 



The term Didymograptus^ as adopted in Great Britain, has usually been 

 applied to such forms as G. ?nuTckiso7iiaiid G. serratulus ; but Prof. M'CoY 

 clearly included species of two very distinct types, since G. sextans and 

 G . furcatus have a different mode of growth, the cellules being on the outer 

 margin of the polypary, and of a different form from those of the first 

 named species and others usually referred to Didymograptus. 



In 1852, Prof. GtEINitz* proposed the name Cladograptus, which, in its 

 definition, included also the two groups of species here noticed, viz. those 

 with the cellules angular and on the inner margin of the stipe, and those 

 with curving indentations upon the outer margin of the stipe. He cites 

 C. ramosus and C. furcatus (Hall, sp.) in his first group, and C. murchi- 

 soni (Beck), C. serra (Gteinitz), C.forschammeri (GtEinitz), C. sextans Siud 

 C. serratulus (Hall, sp.), in his second group. We have in fact precisely 

 the same grouping under Cladograptus that M'CoT has given under 

 Didyinograptus. If the latter term be employed to designate such forms 

 as G. murchisoni (Beck), G. serratulus and G. bifidus (Hall,) and similar 

 forms, then Cladograptus may be used in the restricted sense to designate 

 such forms as G. furcatus^ G. sextans and G. divaricatus (Hall). In this 

 case the term Dicranograptus might be dropped ; since it may not be proper 

 to separate those with the stipe partially divided from those entirely 

 divided, where the cellules are similar in form. Such a disposition of the 

 generic terms willsatisfy the claims of Prof's M'CoT and Geinitz, each 

 one having in his proposed genus included the two groups of species. t 



In 1858, Mr. Carruthers, without knowledge of Prof. Geinitz's 

 Genus Cladograptus, proposed the same name for a form of graptolite 

 found in the shales of Dumfries-shire. In the typical species, the zoophyte 



* Die Versteinerungen der Grauwacken formation in Sachsen, etc. Heft 1, Die Grap- 

 tolithen, pp. 29-32. 



f I have heretofore used the term Didymograptus in its application to such forms as 

 G. murchisoni, forgetting the original extent of its application by Prof. M'Coy ; and it 

 is only since the preceding pages have been in type, that on rereading the remarks of the 

 latter in the paragraph cited, I have become more fully impressed with the necessity for- 

 some revision of the terms in their application to species. 



