838 



NORTH AMERICAN INDEX FOSSILS. 



Labette formation — lower Coal Meas- 

 ures (middle Carbonic) of Kansas. 



Labium — in Crustacea, the lower lip. 



Labrum — in Crustacea, the upper lip. 



Ladinic — subdivision of marine upper 

 Triassic. 



Ladore — middle Carbonic of Kansas. 



Lafayette formation — Pliocenic of east- 

 ern United States. 



Lake Louise formation — lower Cambric 

 of Canadian Rockies. 



Lamella — a very thin plate-like layer. 



Lamellar — disposed in lamellae or plates. 



Lamelliform — having the form of a leaf 

 or lamella. 



Lamellose — having thin plates or scales. 



Lamina — a thin plate or scale ; also ap- 

 plied to the thinnest distinct layer 

 into which a stratified rock can be 

 separated. 



La Motte sandstone — middle Cambric 

 of Ozark region. 



Lancaster limestone — lower Cambric to 

 lower Ordovicic of southern Pennsyl- 

 vania. 



Lancet-plate — in blastoids, the narrow 

 plate running the entire length of the 

 middle of each ambulacrum. 



Lappet — a pendent. 



Lateral lappet — in some ammonoids, 

 one of the lateral, forwardly di- 

 rected projections of the aperture; 

 called also lateral crest (see Fig. 

 1452). 



Laramie formation — upper Cretacic 

 (Continental) of Great Plains. 



Larva — the early form of some animals 

 before they assume the mature shape, 

 as the caterpillar stage. 



Larval — referring to the larva. 



Lateral gemmation — budding from the 

 sides, as in some corals. 



Lateral teeth — ridge-like projections on 

 either side of the beak, in the interior 

 of pelecypod shells. 



Latilamina — the union of several hori- 

 zontal laminae in the hydrocorallines 

 to form a comparatively thick layer 

 (see I., 36). 



Laurel limestone — Niagaran of Ten- 

 nessee. 



Lawrence shales — upper Carbonic of 

 Kansas. 



Leadville limestone — Mississippic of 

 west central Colorado. 



Lebanon limestone — middle Ordovicic 

 of Tennessee. 



Leclaire limestone — Niagaran of Iowa. 



Leroy shales — upper Carbonic of 

 Kansas. 



Lewistown limestone — upper Siluric of 

 Pennsylvania. 



Lexington division — basal upper Ordo- 

 vicic of the Cincinnati region. 



Ligament — in pelecypods, the external 

 structure for opening the valves (see 

 I., 362). 



Lignitic — lower Eocenic of Gulf region ; 

 see Chickasawan. 



Limb — in trilobites, see cephalic limb, 

 and Fig. 1586. 



Lime Creek shales — upper Devonic of 

 Iowa. 



Linden beds — Helderbergian of western 

 Tennessee. 



Lines of growth — see growth lines. 



Lingual — referring to the tongue. 

 Lingual ribbon — see radula. 



Linguiform — tongue-shaped. 



Linguloid — tongue-shaped ; like Lingula 

 (see I., 178, 3). 



Lips — in univalve shells, the outer and 

 inner margins of the aperture. 



Lira; — ridges or plications on the inside 

 of the outer lip of some gastropod 

 shells, as Nerinea. 



Listrium — in brachiopods (as Orbicu- 

 loidea and some others of the Neo- 

 tremata), the plate closing the pro- 

 gressive track of the pedicle opening, 

 posterior to the apex of the pedicle 

 valve. 



Lite — of stone (from Greek lithos, 

 stone ; dropping of h due to conform- 

 ity with the unrelated suffix ite). 



Lithic — pertaining to stone. 



Lithodesma — in pelecypods, the acces- 

 sory calcareous piece strengthening 

 the resilium (as in Liopistha, Cuspi- 

 daria). 



Little Falls dolomite — lower Ordovicic 

 of Mohawk Valley. 



