IUI.OMTIC8. 7M7 



M..tr on Oruru.| 



glabolla is eontmuoii* with t!u> l>n>.id frontal margin of t he ri>|>lialon. Of American 

 species representing this suligenns we may cite: C.apollo and C. mercurius Billings, 

 from the Quebec group, < ;-.// v \Valcott, from the Trenton limestone and C.scofieldi 

 Clarke, from the Galena shales. 



In l'*>-n.l.<{>li.rrexochn8 the Isabella is very eonvex, the thinl lateral furrow 



>tronger than the others, and the third lobe larger and not separated from the body 



of the glahella. The pygidium bears eight marginal spines of subequal length. 



Under this division may be \>\. i>rHticns Hillings, of the Quebec group, and /'. 



'/-i'> Clarke, of the Trenton limestone. 



:konskin Schmidt, has the glabellar furrows very oblique posteriorly, 

 the glahella m<>~t mnvex In-hind and usually produced into a posterior spine; 

 the third furrow is the strongest and the third lobe is not separated from the body. 

 To this division may be referred Millings' C. ylaucus, and C. perforator, of the 

 Quebec group, C. satyrus, of the Chazy limestone, and C. numitor of the Hudson 

 Kiver group. 



Schmidt includes among these subgenera. SpAanMOTjpfc Angelin, in which the 

 anterior portion of the glabella, embracing the frontal lobes and the first and second 

 lateral lobes, becomes extremely convex and subspherical, without traces of lateral 

 furrows. The third lobes only are apparent, and these quite obscure. 



( if the foregoing divisions, all except Pseudosph<rrejcochufi have a pauci-annulate 

 hum. with u-nally two or three annulations and ribs, and the first pair of ribs 

 much the largest and extended at their free extremities far beyond the rest In 

 Pscudosplurracochus the eiyht free po'inte of the pygidial ribs are sharp and angular. 

 In Ki-rnptoehile Corda, there are but sis of these extensions and they are flat, broad 

 and blunt at their extremities, and do not extend beyond the general marginal arc; 

 while in ('rtnhtcrphalus Salter. these are likewise six in number, but narrow, 

 incurved, distant, and acute. The structure of the glahella in Eccoptochile clariyern 

 Corda, the type of the subgenus, is essentially similar to that of Ceraurus, though 

 the glabella is rather more rotund and ovoid; hut in Crotaloctphalus there is a large, 

 convex and protuberant frontal lobe. The first and second lobes are short and 

 horizontal, and the third or basal lobes isolated by the union of the third glabellar 

 furrows with the occipital groove. Sceoftockilt is represented in the Hudson KJV.M 

 fauna by Ceraurus icarus (Billings) Meek. Of the typical Crotalocephalus we 

 probably have but one representative, the C. ni<"/ < I [all, of the Niagara shales 



of Lockport and Rochester. N. V . and the raagnesian limestones of Illinois and 

 ousin. 



-47 



