V 



BRYOGRAPTUS. 87 



Gemis BRYOGRAPTUS, Lapmn-lh. 



1880. Briiograptus, Lapwortli, Aun. Mag. Nat. Hist. [5], vol. v, p. 164, pi. v, fig. 22. 



Polliparij bilaterally subsymnietrical, consisting of two compound main stipes 

 diverging at a small angle from a well-marked sicala, and originating similar 

 compomid or simple stipes either by dicliotomons or lateral division. 

 TJiecx small, of the Llchoi/rdpfiis type, cylindrical or subcylindrical tubes of 



varying inclination, overlapping for a con- 

 Fios. lo a and h.—Bnjograptus Kjcruifi, siderable fraction of their length. 



Lapworth. ... 



I The initial stages of the Bryograptm polypary 



) k are in all I'espects comparable with those of Didymo- 



% jf\\ f/raptus, the difference behig that in the former after 



a longer or shorter period of growth the stipes of 



the first order (Didymoqraptiis stage) give off lateral 



a. Obvci-so view, showing growtli-lmes ' \ ./ ./ j. o / o 



on sicnia. branches from their thecal margins. These lateral 



6. Ee verse view, showing crossing canal. . i mi • 



Both specimens on same slab, branches may be Simple or compouud. There IS great 



Figured Elles, 'Quart. Journ.Geol. . . ,i v •, r .i • xi 



Soc.,' vol. liv, p. 472, fig. 5. Barf, variability withiii the limits or the genus m the 



Skiddaw Slates. Coll. W. A. c ,• ^:_■ i_ ^ i i n i i 



Brend. number 01 stipes ultimately developed, and also m 



the type of the branching. 

 The British Bryograpti fall into two natural serial groups according to the 

 direction of growth of their main stipes ; thus Ave have — 



(1) Dependent Series. — Guuup I. Type B. Kjerulfi. 



B. Kjerulfi, 



var. cnmhrensis. 



(2) Deflexed Series. — Guour II. Type B. dlvetyjens. 



B. divergens. 

 These groups may theoretically be regarded as including In-anched Didynio- 

 grapti of the indentus and deflexiis types respectively. 



Dependent Series. 



Bryograpti in which the main stipes diverge downward, and tend to become 

 approximately parallel. 



Group 1. — Type Br. Kjernlfi. 



Bryograpti in which the main stipes are straight, slender, and of uniform 

 width ; the thecffi are fairly numerous, inclined at low angles, and free for the greater 

 part of their length. 



12 



