372 TWENTIETH REPORT ON THE STATE CABINET. 



young shell, and that they become partially absorbed or almost entirely 

 disappear in the older shells. In specimens regarded as the same species 

 from Indiana and Now-York, the evidence of lamellae is confined to the apex 

 of the valve, and is never observed to extend towards the front of the shell. 

 Formation and locality. This species is common in limestone of the 

 Niagara age, at Racine, Wauwatosa and elsewhere in Wisconsin, and at 

 Bridgeport, Illinois. 



SPIRIFEEA META(n.s.). 

 PLATE 13 (4), FIGS. 12 & 13. 



Spirifer radialus, pars : Hall, Pal. N. Y., Vol. ii, pa. 66, pi. 22. 

 Compare Cyrtia myrtia: Billings, Pal. fossils, p. 165, f. 149. 



Shell small, semioval in outline. Ventral valve low pyramidal : heiglit 

 equal to one half the width, or a little less ; length and height nearly 

 equal ; hinge-line equalling the entire width of the shell ; ventral valve 

 with the area erect or slightly arcuate ; foramen narrow ; deltidium 

 highly convex, perforated near the apex ; sinus broad, nearly one-third 

 the entire width of the valve, deep, and somewhat angular at the bottom. 

 Dorsal valve regularly convex, the mesial fold moderately elevated, 

 very narrow at the umbonal region ; the interior of the ventral valve 

 possessing very strong dental lamellae, which extend more than one-third 

 the length of the valve. Exterior surface of shell marked by a few 

 distinct concentric lines of growth, and fine close radiating striae. 

 This species is of the type of Spirifer trapezoidalis, Dalman ; but 

 difi"ers in its greater proportional width on the hinge, the less elevation of 

 the ventral and more convex dorsal valve. From <S. [Cyrtia) myrtia, Bil- 

 lings, 'it differs in the same particulars, as well as the rounding of the 

 hinge-extremities. In fact these two species, S. myrtia^ B., and S. traye- 

 zoidalis are so closely allied that a careful comparison with each other might 

 lead to an identification. The specimens with elevated area, figured on 

 Plate 22, vol. ii. Pal, N. Y., as varieties of <S. radiata, are of this species. 

 Geological formation and locality. In the limestones of Niagara age, 

 near Milwaukee, Wisconsin, and in the Clinton group, at Rochester, N. Y. 



SPIRIFERA NOBILIS. 

 PLATE 13 (4), FIGS. 14, 15 & 16. 



Spirifer nobilis : Baiirande, icber die Brachiopoden der Silurischen Schichten, von 

 Boehmen. Haidinger, aus den Naturwissenschaftlichen Abhandlungen, Band 2, 

 Tab. xviii, fig. 2, a, b. 



Spirifer racinensis : M'Chesney, Palaeozoic fossils, p. 84. 1861. 



Spirifer inconstans : Hall, Annual Report Geol. Wisconsin, p. 26. 1861. 



Shell transversely elliptical, the length a little more than half as great 

 as the width ; hinge-line two-thirds as long as the greatest width of the 

 shell ; cardinal extremities rounded ; both valves moderately convex, 

 marked by strong angular dichotomizing plications. Dorsal valve most 



