CYRTOGRAPTUS. 



513 



Fig. 359. — Cyt-tograptus Carruthersi, 

 Lapworth. 





number, aiul usually approximately straight and somewhat stiff. Thecse 

 six to eight in 10 mm., like those of M. NUssoni throughout. 

 Description. — The resemblance of the polypary (apart from the cladia) to that 

 of M. Nllsso)ii is very obvious, particularly in the double curvature of the proximal 



portion of the stipe and the characters of the 

 tliecfe. Distally the curvature appears to be more 

 variable, for individuals are of frequent occurrence 

 in which the thecas are on the convex margin 

 instead of the concave. The cladia themselves 

 appear very stiff and straight when compared with 

 the flexed character of the stipe. 



The thecae, both on the stipe and on the cladia, 

 are in all respects like those of M. NiUsoni. 



Horizon and Localities. — Wenlock Shales (Ric- 

 carton Beds), zones of M. riccartonensis and Cyrlog. 

 Limdgreni. 



S. Scotland : Shankendshiels ; Elliotsfield ; R. 

 Slitrig. Welsh Border : Ackley Lane, S. side Long 

 Mountain. 



Associates, etc. — Gyrtog. Carruthersi occurs in the zone of M. riccartonensis 

 associated with M. riccartonensis, M. diiMns, and in the zone of Cyrtog. Lundgreni 

 with G. Lundgreni, M. Flemingl var. com/pactus, and M. duldus. 

 GoUections. — Lapworth, and the Authors. 





Distal thecae of a cladium. Enlarge- 

 ment of part of PI. Lll, fig. 4 6. 



Specific Gharacters of Forms belonging to the Gemts Cyrtograptus. 





C. 



Murchisoni. 



C. 



Lundgreni. 



C. rigida*. 



C. 



symmetricui. 



C. hamatus. 



c. 



Linnarssoni. 



C. Grayi. 



C. 



Carrutherti. 



Character of polypary 



Helicoid 



Sub- 



Slightly 



Stiff, 



Small, 



Slender 



Slender, 



Straight, 





or 



circular 



flexed 



small 



with 



and 



very 



with 





convolute 









strong 



gracefully 



flexed and 



double 





spiral 









curvature 



in 

 proximal 

 portion 



curved 



graceful 



curvature 



in 

 proximal 

 portion 





Many 



Many 



One 



One 



One 



Few 



? Few 



Few 





branched 



branched 



branch 

 only 



branch 

 only 



branch 

 only 



branches 



branches 



branches 



Maximum width 



1'8 mm. 



1 mm. 



lo mm. 



1'5 mm. 



— 



1 mm. 



•6 mm. 



1 mm. 



Character of thecae : 



















1. No. in 10 mm. 



12—10 



10—8 



10—8 



12—9 



8—6 



10-9 



9 



7-8 1 



2. Overlap 



h-\ 



h-h 



\-h 



\-h 



i-i 



Increasing 

 distally 



— 



Slight i 



3. No. of proximal 



Same 



Numerous 



18 



5-8 



11 



7 



Same 



Same 



type 



through- 

 out 













through- 

 out 



through- 

 out 



