Vanuxemia worthenl, LAMELLIBBAKCHIATA. 561 



As it reads I should say that he refers to a species of Cyrtodonta like C. glabella or 

 C. persimilis and not to a Vanuxemia which the shell here under consideration 

 undoubtedly is. The latter differs in at least two important respects from the 

 characters brought out in Hall's description, and either one would in my opinion, be 

 sufficient to defeat specific identity. Thus, he says the beaks are "situated about 

 one-fourth the length of the shell from the anterior end," whereas in Whitfield's 

 niota they are miich nearer the anterior extremity ;' then he gives the impression 

 that the anterior, posterior and basal margins are almost uniformly rounded, while 

 in the present species, the outline is -always more or less quadrangular. Under the 

 circiimstances I might have been justified in proposing a new nalne, but as the 

 questions involved would, still be open (a study of the original of Hall's description 

 alone can answer them), it seemed best to refer to the species provisionally as 

 above. 



Vanuxemia niota Whitfield (?Hall) sp., is closely related to F. hayniana Safford 

 sp., and V. gihbosa Ulrich. From the first it is distinguished by its greater convexity 

 and length, more anterior and larger beaks, and almost rectangular instead of 

 rounded anterior side. The cast figured on plate' xxxviii preserves the impressions 

 of the hinge teeth. The cardinal teeth were rather small, oblique, and numbered 

 four in each valve. The .posterior teeth were slender, nearly horizontal, and three 

 in number. In V. gibbosa the anterior margin forms a wider angle with the hinge 

 line, the shell was a little thickgr, the hinge stronger, and the cardinal teeth larger, 

 not exceeding three in number and less oblique. In artificial casts of that species 

 the anterior muscular scar proved to be comparatively larger, and to project farther 

 anterior to the filling of the beaks, which again are of larger size than in niota. V. 

 wortheni of the Galena belongs to the same group of species but is a much larger 

 and rounder shell, and in casts has more compressed and less incurved beaks. 



Formation and locality.— To^p of the "Lower Blue Beds," and base of the " Upper Buff Beds " of the 

 Trenton formation at Beloit and Mineral Point, Wivsconsin, and Eockton, Illinois. 



Mus. Reg. No. 8321, 8325. 



' Vanuxemia wortheni Ulrich. 



PLATE XXXIX, FIGS. 6 and 7. 



Cypricardites, sp., undet., Meek and Worthen, 1868. 111. Geol. Sur., vol. iii, p. 311. 

 Cypricardites wortheni Uleich, 1888.- Amer. Geol., vol. 1, p, 180. 



Shell large, moderately ventricose, suberect, subcircular, the length a little 

 greater than the hight, the beaks nearly terminal, the dorsal margin almost straight, 

 rather long and with the extremities rounding abruptly, the anterior one scarcely 

 projecting beyond the point of the beaks; the rest of the outline rounded with the 



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