PHYLLOCxRAPTUS. 99 



Phyllograptus, cf. typus, Hall. Plate XIII, figs. 5 a, h. 



1858. 2'hyllograptus tijpus, Hall, Geol. Survey of Canada Rep., 1857, p. 137. 



1865. Phyllograptus typus, Hall, Graptolites of the Quebec Group, p. 119, pi. xv, figs. 1 — 12. 



1868. Phyllograpsus typus, Nicholson, Quart. Journ. Geol. Soc, vol. xxiv, p. 138, yl. v, fig. 16. 



1898. Phyllograptus typus, Elles, Quart. Journ. Geol. Soc, vol. liv, p. 494. 



Stipes united so as to form a polypary with elongate-ovate, l)roacl oval, or 

 obovate outlines. Tliecfe nine to ten in 10 mm., direction of growth and 

 curvature varied, five to six times as long as wide ; in contact throughout 

 their length. Apertural margins concave, mucronate, very oblique. 



Description. — This species is exceedingly variable in form, the known length 

 in our British examples ranging from 31 to 57 mm., and the breadth from 6*3 to 

 10 "5 mm. 



The variation in shape appears to be largely dependent upon the amount of 

 curvature of the thecse, which varies very much in different individuals. 



The thecge are curved throughout the whole length of the polypary ; they are 

 nearly horizontal in the proximal part, but curve back so that the aperture is 

 directed downward. The curvature is less in the middle of the stipe, and the line 

 of the aperture becomes parallel to the general direction of the polypary. Above 

 this the aperture becomes oblique, and the thecse are inclined at higher and higher 

 angles, so that eventually, at the distal end, the apertures of the thecse lie almost 

 perpendicularly with regard to the axis of the polypary, a complete change in 

 direction having thus been effected. 



The sicula appears to be 1"6 mm. in length, and the first theca is developed 

 from near the apical end. There is occasionally a spinous projection from the base 

 of the sicula. 



AiRnities. — The British specimens here doubt- 



Fia. 58.— Phyllograptus typux, Hall. ^' ^ 



fully referred to Phyllograftus tyjms are never so 



^^± large as the typical American form, and do not as a 



^-'M^ rule show the prominent sicular spine so conspicuous 



^^^ ^^ *^^ American examples ; at the same time they 



^M^^ have ])ot the characteristic appearance of Vhyllog. 



^-'-MjIIg^ angustifolius. Although their relative proportions 



W'^^!^'^ as regards length and Avidth are comparable with 



fe>^'^^ the American form, yet the foregoing distinctions 



'\ ^' may possibly some day show them to be a distinct 



f variety. Since, however, our specimens have all 



Specimen from Hall's original locality, ^ecu much affected by clcavago, and are generally 



Britisf 'exampierCr bSow ^ore or Icss indifferently preserved, we prefer to 



GeoioSaisurvr' ^°^^- *^'''"'^'^'''''' refer them provisionally to Hall's spccics. For the 



