852 



NORTH AMERICAN INDEX FOSSILS. 



ing the mouth opening (see Fig. 



1786). 

 Spiralium — a spiral brachidium (see 



Figs, 2203, 392, c). 

 Spire — in gastropod shells, all whorls 



or coils above the opening (see Fig. 



861). 



Imperforate spire — the spire in which 

 the coils are in contact at the cen- 

 ter. 



Perforate spire — a spire in which the 

 axis of coiling is hollow ; this hol- 

 low is the umbilicus. 

 Spiriferoid — shaped like Spirifer (see 



I., 186, 4). 

 Spirogyrate — curved outward. Used in 



reference to the umbos of pelecypod 



shells (see Fig. 633). 

 Spondylium — in some species of brach- 



iopods, the spoon-shaped plate or cup 



under the beak, formed by the union 



of the dental plates (see Fig. 338, A, 



324, g)- 

 Spongin — the horny or fibrous sub- 

 stance of many sponges, as of the 



common bath sponge. 

 Spring Creek limestone — middle Missis- 



sippic of Arkansas. 

 Squama; — scales. In corals, the small 



shelves often present on the inside of 



the wall near the mural pores. 

 Squamous — covered with scales. 

 Stafford limestone — middle Devonic 



(Marcellus) of New York. 

 Star Peak limestone — upper Triassic 



(Karnic) of Nevada. 

 Stellate — star-shaped. 

 Stephen formation — middle Cambric of 



Canadian Rockies. 

 Sternum — the breast-bone. For use in 



crustaceans, see II., 386 ; in insects, 



II., 420. 

 Stigma (plural stigmata) — in insects, 



the external opening of a trachea 



(see Figs. 1722, 4, 5, 6, 8, and II., 



424). 

 Stipe — stalk, branch. 

 Stockbridge dolomite — lower Cambric 



to lower Ordovicic of western New 



England. 



Stolon — an extension of the body wall 

 from which buds are developed. 



Stones River limestone — middle Ordo- 

 vicic of eastern North America. 



Strawn — middle Carbonic (Des Moin- 

 ian) of Texas. 



Strice — fine radiating or concentric lines 

 on the surface of shells. 



Strophomenoid — shaped like Stropho- 

 mena (see I., 184, 4). 



Stylet — for use in Crustacea, see Fig. 

 1696. 



Styliolites — peculiar columnar and 

 striated rock forms seen in some 

 limestones at the junction of two 

 layers. 



Sub — a prefix, meaning under, almost, 

 of low degree, e. g., subangular, 

 rather angular. 



Subcosta — in insects, one of the wing 

 veins (see Fig. 1724). 



Subdorsan — see Fig. 123 1. 



Sub-petaloid — in echinoids, applied to 

 those ambulacra in which the two 

 pore-bearing zones of each ambula- 

 crum separate between the apex and 

 the circumference of the test and 

 do not tend to close in the latter re- 

 gion. These are longer than petaloid 

 ambulacra (see Figs. 1921, d, e, f, and 

 1928, g). 



Sub-quadrangular — between quadran- 

 gular and oval in outline. 



Sub-quadrate — nearly but not quite 

 square. 



Sub-spheroidal — imperfectly spheroidal. 



Subtegminal — in crinoids, applied to 

 the mouth opening when it is be- 

 neath the tegmen (see II., 492). 



Subventran — see Fig. 1231. 



Suffix — one or more letters or syllables 

 united with the end of a word to 

 modify its meaning, e. g., oid, mean- 

 ing in the shape of, in spheroid. 



Silicate — with deep furrows or grooves. 



Sulcus (plural sulci) — a furrow or 

 groove. 



Sumner — division of the Permic of 

 Kansas. 



