J. .H0PKIN80N ON BRITISH GRArXOLITES. 159 



Polypary growing bilaterally from the radicle, and consisting of 

 two primary branches, each of which branches and re-branches 

 from the same side of the periderm on which the hydrothecae are 

 developed, the radicle being on the opposite side. C. linearis, Carr. 

 (P/. riii.,/. 9). 



Genus 8. Dendrograptus, Hall (Grapt. Quebec Group, p. 126). 



Polypary repeatedly branching, in a dichotomous manner, from a 

 thick hydrocaulus composed of the united non-polypiferous bases 

 of the branches, the hydrorhiza probably consisting of a disc of 

 attachment. D. Hallianus, Prout {PL viii., /. 10). 



This genus forms a connecting link between the true graptolites 

 and the genera Callograjitus, Dictyoneina, and Oldhamia. 



Family II. Diprionid^. Polypary with a double series of 

 hydrothec£e. 



Genus 1. Diplograpsus, McCoy (Brit. Palseozoic Foss., p. 7). 



Polypary simple, with hydrothecfe developed alternately from 

 each side the periderm ; each series of hydrothecae having a separate 

 common canal. The solid axis is frequently prolonged distally be- 

 yond the polypiferous portion of the periderm, and terminates at 

 the proximal end in a radicle, sometimes furnished on each side 

 with a short spine. In a peculiar form I found in the Frenchland 

 Burn, Moffat, the prolonged axis is enveloped in a non-polypiferous 

 portion of the periderm. This is a new species, for which I pro- 

 pose the name D. penna. 



Description — D. penna, sp. nov. {PL viii., /. 12). Hydrothecae 

 slightly curved, concave on the distal margin, which is at right 

 angles to the axis, and convex on the proximal, which makes an 

 angle, with the axis, of about 45 degrees. There are 20 hydro- 

 thecEe in the space of an inch, united only at their base. The 

 breadth across the entire polypary is l-8th of an inch. 



D. folium. His. (P/. viii.,/. 13), is a very peculiar form. D. 

 pristis, His. {PL viii.,/. 11), is the most common species of the genus. 



I do not include in this genus the species D. cometa, Gein. 

 Mr. Carruthers suggests that it should be made the type of a new 

 genus, for which I here propose the name Cephalograpsus. 



Genus 2. Cephalograpsus, gen. nov. 



Hydrothecae opposite, tubular, few in number, formed into a head 

 at the distal end of the polypary, and collected into a common 

 canal at the proximal end. C. cometa, Gein. sp. {PL viii., /. 14). 



