160 



J. HOPKINSON ON BRITISH GRAPTOLITES. 



Genus 2. Climacograptus, Hall (Gvapt. Quebec Gr., p. 111). 



Polypary simple, with incised hydrotheca? excavated alternately 

 in each side of the polypary ; the common canal communicating 

 between the two series of hydrothecfe. The solid axis is frequently 

 prolonged distally, and the radicle is sometimes very long and 

 slender. C. scalaris, Linn. {PI. viii., /. 15). C. bicorms, Hall 

 (PL viii.,/. 16). 



The genus Retiolites, a diprionidian form, I do not consider a 

 true graptolite. 



Family III. Monodiprionid^. Polypary with a single and 

 double series of hydrothecse. 



Genus 1. DiCRANOGRAPTUs, Hall (Grapt. Quebec Gr., p. 57). 



Polypary, towards the proximal end with a double series of 

 hydrothec^, dividing distally into two branches bearing hydro- 

 thecse on their exterior margin only. The solid axis is double, 

 bifurcating in the axil of the branches. In D. ramosus, Hall {PL 

 viii.,/. 17), the hydrothecse appear to have the same structure as 

 in Climacograptus. 



Family IV. TsxRAPRioNiDiE. Polypary with a quadruple series 

 of hydrothecse. 



Genus 1. Phyllograptus, Hall (Canada Geol. Surv. Report, 

 1857, p. 135). 



Polypary with four series of hydrothecse arranged in a cruciform 

 manner round a cruciform common axis. Each series of hydro- 

 thec« has its own common canal, not communicating at all with 

 the other series, and in each series the hydrotheca^ are in contact 

 for their whole length. P. angustifolius, Hall {PL viii., /. 18). 



§ IV. Zoological Position. 



Naturalists seem to have almost the same diversity of opinion as 

 to the zoological position of graptolites, now, as they had years 

 ago. Professors McCoy and Wyville Thompson place graptolites 

 among the Sertularian Hydrozoa ; M. Milne Edwards considers 

 they " have more affinity with Virgularia,'' an Actinozoon, '< than 

 with any other recent zoophyte;" Professor Huxley and Mr. 

 Salter refer them to the Polyzoa; while Professor Owen and Mr. 

 Carruthers class them among the Hydrozoa. 



That they are really zoophytes there cannot be the slightest 



