THE AKENIG AND LLAKDEILO KOCKS OF ST. DAVID S. 



633 



Class HYDROZOA, Huxley. 

 Order HYDROIDA, Huxley. 



Division Graptolithina, Bronn. 



Sub- 

 orders. ( 



Sections. 



O 

 O g 



GRAPTOLOIDEA. 



w 1 



On .| 



EETIOLOIDEA 



CORYNOLDEA 

 THAMNOIDEA 



DENDROLDEA 



Families. 

 Monograpticlee 



Nemagraptidae 



Dichograptidse . . 

 Dicranograptidce 

 Diplograptidae . . 



Phyllograptidse .. 



Glossograptidae .. 



i 



} Gladiograptida? .. 



Corynogi'aptidae . . 



ThamnograptidEe 



f Ptilograptidas 



Callograptidse. 



Genera. 



{Rastrograptus*, Barr. 

 Monograptus, Gein. 

 Cyrtograptus, Carr. 

 ( Pleurograptus, Nick. 

 J Amphigraptus, Lapw. 

 •{ Leptograptus, Lapw. 

 j Ccenograptus, Hall. 

 [ Nemagraptus, Emmons. 

 f Didymograptus, M'Coy. 

 j Tetragraptus, Salter. 



Dichograptus, Salter. 



Loganograptus, Hall. 



Clonograptus, Hall. 

 L Clematograptus, Hopk. 

 f Dicellograptus, Hopk. 

 \ Dicranograptus, Hall. 

 ( Climacograptus, Hall. 

 | Diplograptvs, M'Coy. 



d f Gtyptograptus, Lapw. 



gp J Petalograptus, Siiss. 



-2 1 Cephalograptus, Hopk. 

 ^ «2 [^Orthograptus, Lapw. 



Phyllograpttcs, Hall. 



{Glossograptus, Emmons. 

 Retiograptus, Hall. 

 Lasiograptus, Lapw. 

 ( Clathrograptus, Lapw. 

 4 Trigonograptus, Nick. 

 [ Gladiograptus*, Barr. 

 Corynograptus*, Niek. 

 J Thamnograptus, Hall. 

 \ Buthograptus, Hall. 



Ptilograptus, Hall. 

 ( Bendrograptus, Hall. 

 I Callograptus, Hall. 

 Bictyograptus, Hall. 



Subgen. Besmograptus, 

 Hopk. 



The arrangement of the Rhabdophora adopted is that originally 

 proposed , in Mr. Lapworth's paper on an Improved Classification 

 of the Rhabdophora, published in the ' Geological Magazine ' for 

 November and December, 1873. The genera included under this 

 head present among themselves extraordinary morphological diver- 

 sities. The most extreme types, however, appear to be connected by 

 known intermediate forms ; and they constitute collectively a well- 

 marked, compact, natural group. 



* The slight alterations in the terminations of these names have been made 

 with the concurrence of the founders of the respective genera. 



