GLOSSARY. 



827 



Clavicle — in some pelecypods, a heavy 

 internal ridge running downward 

 from the beak ; its posterior end sup- 

 ports the resilium. 



Claytonian — lower Eocenic of Gulf 

 coast (Midwayan). 



Clear Creek limestones — Helderbergian 

 and Oriskanian of Illinois, etc. 



Cleveland shale — upper Devonic of 

 Ohio. 



Cliffwood formation — basal marine Cre- 

 tacic of New Jersey. 



Clinton group — lower Niagaran of east- 

 ern North America. 



Clypeus — see II., 419. 



Cobleskill limestone — upper Siluric of 

 eastern North America. 



Cochran formation — lower Cambric of 

 southern Appalachians. 



Coelome — the general body cavity of an 

 animal as distinguished from all spe- 

 cial cavities, as the intestinal cavity, 

 etc. 



Coenenchyma — in composite corals, the 

 calcareous tissue connecting the dif- 

 ferent individuals, as in Oculina. 



Ca'nosteum — the coral-like calcareous 

 structure of some of the hydrocoral- 

 lines, as Millepora. 



Coeymans limestone — division of Hel- 

 derbergian, lowest Devonic of North 

 America. 



Coldbrookian — the basal lower Cambric 

 of the Atlantic coast. 



Coldwater shale — lower Mississippic of 

 Michigan — equivalent to Cuyahoga 

 shale of Ohio. 



Colorado formation — lower Cretacic of 

 the interior of North America. 



Columbites beds — lower Triassic of 

 Idaho. 



Columbus limestone — middle Devonic 

 of Ohio. 



Columella — a small column. In corals, 

 a small rod at the center of the cup 

 (see Fig. 119, upper) ; in gastropods, 

 the axis of union of the successive 

 coils (see Fig. 856, d). 



Columellar — referring to the columella. 



Columellar lip — in gastropods, the in- 

 ner lip. 

 Columellar folds or columellar plicce 

 — ridges or plications upon the in- 

 ner lip of some gastropod shells 

 (see Fig. 1153)- 



Columnar — formed in columns. 



Comanche Peak limestone — a division 

 of the Fredericksburg or middle Co- 

 manchic. 



Commensalism — the state of living with 

 another organism, either as a tenant 

 or as a co-inhabitant, but not as a 

 parasite (see I., 36). 



Como beds — upper Jurassic of Wyo- 

 ming. 



Compound eye — in many arthropods, 

 such as the common house fly, the 

 Cray fish and the trilobite Phacops 

 (Fig. 1636, b), very many single eyes 

 each complete in itself are crowded 

 together into two aggregations, the 

 compound eyes. 



Concavo-convex — with one side con- 

 cave and the other convex. Shells of 

 brachiopods are normally concavo- 

 convex, with the brachial valve con- 

 cave and the pedicle valve convex ; 

 shells are reversed or resupinate 

 when the opposite condition is true. 



Conchiolin — the organic part of the sub- 

 stance of a shell left after the re- 

 moval of the lime carbonate by acids. 



Conemaugh formation — a division of 

 the upper Carbonic of eastern North 

 America. 



Confluent — blended so that the line of 

 separation is not visible. 



Coniform — cone-shaped. 



Connoquenessing sandstone — upper 

 Kanawha of Ohio and western Penn- 

 sylvania. 



Conococheague limestone — upper Cam- 

 bric of Pennsylvania-Maryland. 



Conoidal — nearly but not quite conical. 



Conotheca — in Belemnoidea, see II., 24. 



Convolute — Said of the spires of those 

 gastropods and cephalopods in which 

 the later whorls entirely conceal the 

 earlier whorls (see Fig. 1105). 



