CYRTOGRAPTUS. 



)11 



AffiiiUies. — C/jrtofj. hamalas recalls G. rhjidiis in general form, but is stouter in 

 the proximal region, while the terminal tliecae of both stipe and cladium are of a 

 different character. 



Horizon ami Localities. — Wenlock ? 



Ireland : Townland of Grarran Grena, Tipperary. 



Collection. — Geological Survey of England and Wales. 



Figs. 357 a and b. — Cyrtograptus Linnars 

 soni, Lapworth. 



f 



Cyrtograptus Linnarssoni, Lapworth. Plate LI, fig. 4. 



1880. Cyrtograptus Linnarssoni, Lapworth, Ann. Mag. Nat. Hist. [5], vol. v, p. 158, pi. iv, figs. 12 a 



and b. 

 1900. Cyrtograptus Linnarssoni, Elles, Quart. Jouru. Greol. Sjc, vol. Ivi, pi. xxiv, fig. 3 a. 



Polypary several centimetres in length; stipe slender and gracefully curved 

 throughout, with small recurved proximal portion, widening slightly from 

 origin until the maximum breadth of 1 mm. is attained, with two or more 

 gracefully curved slender cladia agreeing in all details with the distal por- 

 tions of the stipe. Thecse ten to nine in 10 mm., sub-triangular in the 



proximal t)ortion with reflexed apertural 

 margms, becoming gradually more tubular 

 with greater overlap distally. 

 Description. — -The polypary is characteristically 

 slender Avith graceful curvature in both stipe and 

 cladia ; there is no very marked increase in width, 

 the breadth at the origin being almost as great as 

 that in the distal portion of the polypary. There 

 are usually two cladia only, though there may be 

 more, and occasionally these may show cladia of a 

 second generation. There is a tendency to slight 

 spiral growth in the extreme proximal portion of 

 the stipe, so that the initial part of the polypary is 

 rarely found on the same layer of rock as the cladia 

 and distal portion, and this makes complete speci- 

 mens difficult to obtain. 



The sicula has a length of about 1 mm. and 

 there are commonly five or six thecse before the first cladium is given off. 



The change from the sub-triangular form to the tubular form of tlieca takes 



place very gradually in passing from the proximal to the distal portion of the stipe. 



Affinities. — The short slender proximal portion, the graceful curvature of the 



stipe and cladia, and the form of the thecjfi, render this species easy of separation 



from all others included under this genus. 



Horizon and Localities. — Wenlock Shales (zone of GijrUxj. Linnarssoni). 



67 



^/ 



^M 







4! 

 til 



a. Proximal portion, showing sicula, 

 thecse of stipe, and cladium. Enlarge- 

 ment of part of PI. LI, fig. 4. 



b. Distal thecae of the cladium. En- 

 largement of part of PI. LI, fig. 4. 



