CHEIRURUS. 61 



Subgenera, 



Crotalocephalus, Cheirurus, Eccoptoclnle, Actinopeltis ; and most probably Sp/iarexo- 

 c/tus, ought to be added. It is simply convenient to keep this last as a distinct genus. 



Subgenus — Crotalocephalus, Salter, 1853. 



Glabella oblong, broadest in front, with furrows continuous across. Body-rings 11, 

 nodular. 



Devonian. Upper Silurian. 



Subgenus — Cheirurus, Auctorum. 



Glabella broadest in front, with furrows all distinct, but not meeting across. Body- 

 rings 11, nodular. 



Upper and Lower Silurian. 



Subgenus — Eccoptochile, Corda, 1847. 



Glabella ovoid, not much inflated, with long furrows. Body-rings 12, grooved 

 imperfectly, not nodular. 



Upper Cambrian ? Lower Silurian. 



Subgenus — Actinopeltis, Corda, 1847. 



Glabella ovoid, often much inflated, and with the anterior furrows nearly obsolete. 

 Body-rings 10, grooved imperfectly, subcylindrical, not nodular. 



Many of these lead directly to the genus Splicer exochus, which has only the characters 

 of Actinopeltis in an exaggerated form. Its labrum is like that of Actinopeltis, and its 

 pleurae are subcylindrical, and the body-rings 11. 



Subgenus — Crotalocephalus. 

 Ch. (Crotalocephalus) articulatus, Milnst. ? PI. VI, figs. 7, 8. 



Calymene articulata, Miinster. Beitriige, vol. iii, pi. v, fig. 7, 1840. 



— Steenbergii, Phillips (not Miinster nor Boeck) . Pal. Foss.,fig. 24/, 1841. 



Calymene — Burmeister. Organ. Trilob., 2nd ed., p. 116, 1846. 



Cheirurus articulatus, Salter. Decade Geol. Surv. 7, pi. i, art. 1, p. 10, 1853. 

 — — Id. Morris's Catal., 2nd ed., p. 103, 1854. 



