560 THE PALEONTOLOGY OP MINNESOTA. 



[Vanuxemla atoupta. 



ridge, and longer hinge line.^ Of associated species, Crytodonta glabella Ulrich, has a 

 similar outline, but there is no relationship between them since that species is as 

 true a Crytodonta as this is a Vanuxemia. 



Formation and Locality.— In the upper part' of the middle third of the Trenton shales, Goodhue 

 county and Chatfleld, Minnesota. 



Vanuxemia abbupta n. sp. 



PLATE XXXVIII, FIG. 39-44. 



Shell a little beneath the tiiedium size for the genus averaging 20 mm. high and 

 24 mm. long; rounded or subquadrate in outline, with subterminal beaks, tumid in the 

 umbonal region and in front of the center, the anterior' end very obtuse, the surface 

 in the upper part rounding abruptly inward to the edges of the valves so that in a 

 side view of casts of the interior the sharply defined anterior muscular scar is quite 

 hidden beneath the filling of the umbones. Hinge line straight, long, terminating 

 more or less abruptly posteriorly; posterior margin broadly rounded, occasionally 

 nearly erect, usually a little oblique; anterior side truncated above, rounding below; 

 base rounded. Xlasts have full and rounded and well incurved beaks, and the con- 

 vexity of the surface continues without a sign of the sulcus and ridge exhibited by 

 the casts of so many species of this genus. As near as- can be determined from the 

 impressions, the hinge plA,te was narrow and bore two, in one case apparently three 

 slender posterior lateral teeth and two cardinal teeth in each valve. Pallial line and 

 posterior muscailar impression very obscure. Surface almost smooth, the best 

 specimens only showing remains of fine concentric lines. 



This well marked species is believed to be related to F. nana and V. hayniana, 



but the subterminal beaks and obtuse anterior end will distinguish it at once. Prom 



V. terminalis of the lower Trenton, which certainly i§" also very much like it and 



perhaps a more natural ally, it is separated by the more erect form. 



Formation and locality.— 'M.iAile Galena, Fillmore and Goodhue counties, Minnesota. 



Vanuxemia niota Whitfield (?IIaU). 



PLATE XXXVIII, FIG. 35. 



fOypricardites niota Hall, 1861, Rep. Supt. Geol. Sur., Wis., p. 20; also 1862, Geol. Rep., Wis., vol. i, 



p. 38, Fig. 8, p. 438. 

 Cyprioardites niota Whitfield, 1882, Geol. Rep., Wis., vol. iv, p. 208. 



I am very much inclined to doubt that this species, a specimen of which was 

 submitted to Prof. Whitfield, is the same as the one described by Prof. Hall. If it is, 

 then the original description is anything but accurate.* 



* Hall's .original description of Cryprieardites niota reads as follows ; " Shell broadly suftovate, broadest at the posterior 

 end; umbones very gobbous, bealcs incurred, little elevated, situated about one-fourth of the -length of the shell from 

 the anterior end. Cardinal line straight or little curved ; anterior, posterior and basal margiiis rounded.' Anterior muscular 

 impression situated near the cardinal line, well defined; posterior imprint obscure. Surface of the shell marlied by oon. 

 centric lines of growth. This species differs from 0. rotundata In being more oblique, in the straighter cardinal line, and' less 

 ventricose form. It is intermediate between that species and C. ventrpeosa, from which It dlflers in less obliquity and the 

 greater length from beak to base." "Length, one inch and a quarter; hight, one inch." 



