560 THE PALEONTOLOGY OF MINNESOTA. 



[Vanuxemla abrupta. 



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 ABRUPTA n. sp. 



PLATE XXXVIII. FIG. 39-44. 



Shell a little beneath the medium 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. Casts 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 plate 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 muscular 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 V. nana and V. hayniana, 

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

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

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



Formation and locality. Middle Galena, Filloiore and Goodhue counties, Minnesota. 



VANUXEMIA NIOTA Whitfield (?Hall). 



I'i.ATE XXXVIII. FIG. 35. 



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



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

 Cypricardites 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.* 



Hull's <" 'riptlim nf ' < i reads as follows: Shell broadly siiboviite. lirnaili'-i at I lie post, i-ii.r 



,.,,,1; in,,! es very i.">bbous. beaks inemved. little elevated, situated about one-four! li nf the !enj:lli of the shell nun 



the anterior end. ( ardlnal line st r;ilsht <M ' litt 1. rui \ ed ; anterior, posterior and basal margins rounded. Anterior inns nlar 

 impression si mated near the eardinaLllne, well detin.-d; posterior Imprint obscure. Surfai-e of I he shell marked h.\ eon 

 ITU trie Mm- i if growth. This species differs from ('. rotunilnln in lie lie.- more oblique, in the straight er cardinal line. Bud less 

 ventrlcose form. It Is intermediate between that species and (.'. ri-nlrrrniui. from which It dllicrs In less obliquity and the 

 greater length frmn beak t" base." Length, one ineh and a iiuartur; hlght. one inch." 



