T. H. Clark — A New A gelacr initid. 71 



Cameyella multibrachiata has rays I, II and IV all 

 bifurcated ; C. raymondi has ray II bifurcated. C. val- 

 courensis differs from these two species in having no 

 rays bifurcated. Moreover both C. multibrachiata and 

 C. raymondi are small species, the types being 10mm. 

 and 8mm. in diameter respectively. C. valcourensis 

 lacks the heavy border of large thick plates which char- 

 acterizes C. billingsi; the latter species, like C. youngi, 

 possesses straight rays. C. chapmani has a border of 

 small plates while the border plates in C. valcourensis 

 are large ; in C. chapmani all the rays are contra-solar. 

 The interradii of C. platys are covered by small imbricat- 

 ing plates, but in C. valcourensis these plates are large. 

 There is a strong curvature to all the rays in C. pilea, so 

 much so that the tips of the rays become parallel, or 

 nearly so, to the peripheral ring. Rays I and V in C. 

 valcourensis show only slight curvature. 



Table I. 

 'Range of North American Ordovician A gelacr initidce. 



I ^ 



■ I 1 



5 . ^ « 



£3 ^-» T* m *-< ' — r ? — i ^ ?-i i— h J-i 



-3 N ^ ^ O n^ £> £ JO <D n^ 0> 



Genus Lebetodiscus. 



L. dicksoni Billings * 



L. lorif ormis Eaymond * 



Genus Cameyella. 



C. pilea (Hall) * 



C. vetusta (Foerste) * 



C. raymondi Clark * 



C. youngi (Eaymond) * 



C. chapmani (Eaymond) * 



C. platys (Eaymond) * 



C. billingsi (Chapman) * 



C. multibrachiata (Eaymond) * 



C. valcourensis sp. nov * 



Genus Isorophus. 



I. faberi (Miller) 1 * 



I. austini (Foerste) 2 * 



I. cincinnatiensis (Eoemer) * 



I. holbrooki (James) * 



I. inconditus (Eaymond) * 



1 Aug. F. Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. 17, p. 441. 



2 Aug. F. Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. 17, p. 444. 



Museum of Comparative Zoology, 

 Cambridge, Mass. 



