46 MISSISSIPPIAN BRACHIOPODA 



CRANIA ROWLEYI Gurley 

 Plate I, Figs. 37-39 



1883. Crania Rowleyi Gurley, New Garb. Foss., Bull. No. 1, p. 3. 



1892. Crania Rowleyi Hall and Clarke, Pal. N. Y., vol. 8, pt. 1, pi. 4H, fig. 



13. 

 1908. Crania rowleyi Rowley, Mo. Bureau Geol. and Mines, vol. 8, 2nd ser., 



p. 73, pi. 17, figs. 3-4. 



Description. Shell small, subcircular or subovate in outline, attached 

 to shells of brachiopods or molluscs. The dimensions of a normal speci- 

 men are : maximum diameter 10 mm., convexity of brachial valve 2.5 mm. 



Pedicle valve not observed, firmly attached to a foreign object. 



Brachial valve conical, the apex of the cone a little eccentric, the sides 

 of the valve from the apex to the margin nearly straight or very gently 

 convex. Surface marked by fine, abruptly elevated, radiating costae, 

 which increase regularly by intercalation, and about three of which oc- 

 cupy the space of 1 mm. Crossing the costse upon shells of normal size, 

 there are usually two or three more or less conspicuous, concentric lines 

 of growth occurring at nearly regular intervals. 



Remarks. This little shell belongs to that division of the genus Crania 

 characterized by distinct radiating costae It is confined to the Louisiana 

 limestone fauna, so far as known, and need be compared only with 

 C. blairi of the Chouteau limestone which has sometimes been considered 

 as a synonym. C. rowleyi, however, is a smaller shell, with more eccen- 

 tric apex, and with somewhat coarser costse. 



Horizon. Louisiana limestone. 



CRANIA BLAIRI Miller 

 Plate I, Figs. 34-36 



1892. Crania Uairi Miller, Adv. Sheets 18th Rep. Geol. Surv. Ind., p. 56. 



pi. 9, figs. 5-6. 

 1894. Crama Uairi Miller, 18th Rep. Geol. Surv. Ind., p. 310, pi. 9, figs. 



5-6. 



Description. Shell small, subcircular or subovate in outline. The di- 

 mensions of a normal example are : maximum diameter 14 mm., convexity 

 of brachial valve 5 mm. 



Pedicle valve attached to foreign objects not observed. 



Brachial valve conical w r ith the apex of the cone subcentral, the sides 

 of the valve from the apex to the margins gently convex. Surface marked 

 by fine, sharp, radiating costae which increase by intercalation and which 

 are often somewhat flexuous, especially on the outer half of the valve, 

 three or four usually occupying the space of 1 mm. Crossing the radiat- 

 ing costae, one or more inconspicuous, concentric lines of growth are some- 

 times present, but they are never a strongly marked feature. 



