SPIRIFERINA 293 



1899. Spiriferina. solidirostris Girty, Mon. U. S. Geol. Survey, vol. 32, 



p. 545, pi. 71, fig. 10a. 

 1901. Spiriferina solidirostris Weller, Trans. St. Louis Acad. Sci., vol. 11, 



p. 198, pi. 20, figs. 2-4. 

 1903. Spiriferina solidirostris Girty, U. S. Geol. Survey, Prof. Paper No, 



16, p. 294, pi. I, figs. 3-4. 



Description. Shell below medium size, wider than long, the greatest 

 width along the hinge-line, the cardinal extremities angular. The dimen- 

 sions of a pedicle valve are : length from umbo to front margin 12.5 mm., 

 width along the hinge-line 15 mm., convexity 6.7 mm., height of cardinal 

 area 3 mm. 



Pedicle valve with a broad, prominent umbo, the surface curving rather 

 abruptly to the anterior margin and sloping to the cardinal extremities 

 with a slightly sigmoidal curve, becoming slightly compressed towards 

 the cardinal extremities; mesial sinus sharply defined, originating at the 

 beak, of medium width and depth, marked in the bottom by a single, 

 angular, median plication which originates in the posterior half of the 

 valve ; the beak pointed and strongly incurved ; the cardinal area rather 

 high, nearly flat below and lying almost at a right angle to the plane 

 of the valve, becoming concave above and strongly arched to\vards the 

 beak, the apical portion sometimes being so much incurved as to be 

 directed almost towards the hinge-line; delthyrium rather large, usually 

 higher than wide, often retaining the pseudodeltidial covering towards 

 the apex; lateral slopes marked by from six to eight, strong, simple, 

 rounded plications which originate along the cardinal margin, those 

 bounding the sinus are the strongest, the lateral ones becoming pro- 

 gressively smaller towards the cardinal extremities. Internally the apical 

 portion of the valve is much thickened and solidified, and the rather 

 strong median septum extends to about the middle of the valve, the 

 dental plates are rather short and thick and the muscular scars are 

 inconspicuous. 



Brachial valve depressed convex, much less convex than the opposite 

 one, the greatest convexity usually near the middle, the surface some- 

 what compressed towards the cardinal extremities ; the mesial fold sharply 

 defined, originating at the beak, moderately elevated above the general 

 surface of the valve, flattened on top and marked by a single, simple, 

 mesial furrow ; the beak inconspicuous and scarcely extending beyond 

 the cardinal margin; the cardinal area very narrow; lateral slopes 

 marked by plications similar to those of the opposite valve and alternate 

 with them. Internal characters- not observed. 



Besides the plications each valve is ornamented by regular, concentric, 

 sublamellose, imbricating markings, about two or three of which occupy 

 the space of one millimeter. The shell structure is punctate. 



