834 



NORTH AMERICAN INDEX FOSSILS. 



Genundewah limestone — upper Devonic 



of New York. 

 Genus — the first of the two or three 



names applied to a single fossil (see 



L, 5). 

 Georgetown limestone — Washitan or 



upper Comanchic of Texas. 

 Georgia shales — lower Cambric of 



northern Appalachian region, 

 Georgian — a term for the lower Cam- 

 bric of the Pacific and Appalachian 



provinces. 

 Gerontic — old (see ontogeny). 

 Gibbous — swollen, very convex. 

 Gills — the respiratory organs of mol- 



lusks and higher marine animals. In 



pelecypods, see L, s^^' 

 Girardeau limestone — basal Siluric of 



the Ozark region. 

 Glabella — in trilobites, the central and 



most prominent portion of the cepha- 



lon, bounded by the fixed cheeks ^see 



Fig. 1542). 

 Glabellar — referring to the glabella. 

 Glen Rose limestone — subdivision of 



Trinitan or lower Comanchic of 



Texas. 

 Globe limestone — upper Devonic and 



upper Carbonic of Arizona. 

 Glomerate — growing in dense heads or 



clusters, generally of an irregular 



character. 

 Gonopolyp — a reproductive polyp of 



Hydrozoa. 

 Gonotheca — the protective covering of 



a reproductive polyp (see Fig. 31). 

 Goodland limestone — Fredericksburgian 



(middle Comanchic) of northern 



Texas. 

 Gower limestone — Niagaran of Iowa. 

 Grainger shale — Devono-Mississippic of 



southern Appalachians. 

 Grand Greve limestone — Oriskanian of 



eastern Canada. 

 Grand Gulf group — middle Oligocenic 



of Gulf states. 

 Grand Rapids group — upper Mississip- 



pic of Michigan. 

 Graneros shale — lower Cretacic (Ben- 

 ton) of Colorado, etc. 



Granulated — having small and even ele- 

 vations resembling grains. 



Granulose — bearing or resembling 

 grains or granules. 



Greenbrier limestone — Upper Mississip- 

 pic of Appalachians. 



Greenfield dolomite — basal bed of lower 

 Monroan of Ohio, etc. 



Greenhorn limestone — subdivision of 

 the Benton (Coloradoan). 



Green River group — continental Eo- 

 cenic of Wyoming. 



Greer formation — Permic of Oklahoma 

 and Texas. 



Gregarious — living in colonies. 



Grenville limestone — upper Chazy of 

 Ottawa River region. 



Groove — in trilobites, see Fig. 1542. 



Growth lines — in shells, lines marking 

 the periodic increase in size (see I., 

 171). 



Guadalupian — Permic of western Texas 

 and New Mexico. 



Guard — the calcareous, posterior por- 

 tion of the internal shell of Belem- 

 noidea. It is cigar-shaped. Called 

 also rostrum (see Fig. 1512). 



Guelph — upper division of Niagaran. 



Gyroceracones — loosely coiled, Nauti- 

 loid cephalopod shells, with no im- 

 pressed zone (see Figs. 1293, 1298). 



Habitat — the area or region in which 

 an animal or plant naturally lives. 



Hamburg limestone — middle Cambric 

 of Nevada ; has also been used for a 

 bed in the Kinderhook of the Missis- 

 sippi Valley. 



Hamilton beds — middle Devonic of 

 eastern United States. 



Hannibal shales — middle division of 

 Kinderhook, Mississippi Valley. 



Harding sandstone — upper Ordovicic, 

 Rocky Mountain region. 



Hardiston quartzite — lower Cambric of 

 New Jersey. 



Harpers formation — lower Cambric of 

 Pennsylvania and Maryland. 



Harrodsburg limestone — middle Missis- 

 sippic of Indiana. 



