558 C. Lapii'orth — On British GraptoUtes. 



nature, but must place tlaem in immediate proximity in the general 

 arrangement. On the other hand, the two groups differ so greatly 

 as a whole, in the early stages of their development, and in 

 the general ultimate structure of the adult polypary, that we are 

 certainly justified in considering them as forming two separate 

 sections of the Bhabdophora. To the first of these sections the term 

 GBAPTOLiTiDiE ^ sliould be restricted. For the second section I pro- 

 pose the title of Eetioloidea. 



It is impossible on the present occasion even to glance at the re- 

 maining differences in matters of detail between the present and 

 former schemes of classification. One only will finally be noticed. 

 The genus Glossograptus as here received includes all those peculiar 

 forms furnished with the lateral appendages referred by Hall, Hop- 

 kinson, and Allman to the reproductive system of the Graptolites. 

 While their apparently numerous points of affinity with the true 

 Graptolites (Graptoloidea) cannot for a moment be denied, yet their 

 internal structure furnishes incontrovertible evidence that they are 

 most intimately related to the Eetioloidea. 



Future alterations in the arrangement of the BJiahdophora will in 

 all likelihood be mainly dependent upon elements of classification 

 derived from our improved knowledge of their various methods of 

 multiplication and reproduction. Whatever evidence is at present 

 afforded by our very limited acquaintance with these subjects has 

 been, from its very vague and uncertain character, virtually ignored 

 in the Table. The indications it gives of defects in the present 

 scheme bear wholly upon the families Dijplograptid(g and Glosso- 

 graptidce. Many of the species here associated with those of the 

 former will probably have to be eliminated and located elsewhere, 

 while the latter will have to be divided among several distinct 

 families. 



There are two genera of Silurian fossils unnoticed in the Table, 

 which may eventually have to be included in the Bhabdophora. The 

 genus Corynoides ought perhaps to be considered morphologically as 

 a Graptolite, in which development never proceeds beyond the sicula 

 stage. The polypary in Thamnograptus (Hall) appears to be furnished 

 with a dorsal filament or solid axis, which enters into all the ramifi- 

 cations of the branches. 



APPENDIX. 

 Description of new genera and species. 



Sub. order: Bhabdophora (Allman). 

 Sect. I. — Graptolitid^. 

 Fam. : Nemagraptid^. (Hopkinson). 

 Leptograptus (gen. nov.). (Gr. A.67rT09, slender.) 

 Polypary consisting of two simple, slender, flexuous, monoprioni- 

 dian branches, proceeding in opposite directions from the major 

 extremity of a well-marked persistent sicula, which is sometimes 



^ There are so many natural and obvious reasons at present for regarding this term 

 as synonymous with Allman's terra Ehabdophora, that it might prove of service to 

 employ the term Graptoloidea for this section, as a second and convertible designation. 



