THE PALEONTOLOGY OF MINNESOTA. 



[Aparoliitcs ellipticus. 



APAKCHITES ELLIPTICUS, n. sp. 



PLATE XLIII, FIGS. 15-17. 



SI/.K. (E. C.) Length 1.97 mm.; hight 1.35 mm.; thickness u.'.)f> mm. In the largest specimen the 



length is 2.5 mm. 



Carapace rather large for the genus, almost regularly elliptical in outline, the 

 dorsal margin of the left valve more arcuate and projecting above that of the right; 

 edges beveled all around but in the lower part the bevel is turned into a groove by 

 the thickening of the contact edges; surface of valves smooth and rather uniformly 

 convex. 



This form, though the hinge is shorter than usual, must still be considered as a 

 typical species of the genus. The general expression of the carapace is much as in 

 the associated Leperditella persimilis, but it is somewhat longer, has no dorsal angle, 

 and its valves do not overlap. I know of no American species of Aparchites with 

 which it need be compared, the elliptical outline being distinctive, but there are 

 several in the Upper Silurian deposits of Europe that are not far removed. Particu- 

 larly is this true of the A. simplex, from Gothland, described by Prof. Jones in the 

 Ann. and Mag. Nat. Hist., ser. 6, vol. iv, p. 272. That species, however, is smaller 

 (0.9 mm. in length), relatively shorter, and apparently without bevelled edges. Some 

 of the varieties referred to A. (Primitid) muccoyii Jones and Holl, are very near, if not 

 identical. But I am not willing to admit the latter without a direct comparison of 

 specimens. 



Formation and locality. Middle third of the Trenton shales, Minneapolis, Minnesota. An imper- 

 fect left valve from the Galena shales near Cannon Falls, may belong to this species, but it appears to 

 have been relatively longer and somewhat narrower anteriorly. 



APARCHITES GRANILABIATUS Ulrich. 



PLATE XLV. KIGS. lil-23. 



I. < I if nl it in grnniluliiata ULKicii, 1802. American Geologist, vol. x, p. 267. 

 SI/.K. (L. V.) Length 2.1 nun.; hight 1.5 mm.; thickness 0.0 mm. 



Valves liigh, very little oblique, ventricose in the lower half, somewhat flattened 

 in the upper; outline almost semicircular in the lower two-thirds, the ventral curve 

 being unusually convex; dorsal margin straight, about three-fourths as long as the 

 valve, with angular extremities; border scarcely defined, set with small but promi- 

 nent papilla-; free <c]g.>s Ixivv.lltnl strongly inward. Surface covered with minute, 

 regularly arrangm! granules; mur the center a small raised spot.* 



Recent comparisons have, demonstrated the necessity of excluding species of this 

 typ<! from Lrj>i-i-t/it!<i. They have shown further that the typical species of Aparchites 



In I hr MI . : i |ii ion I In' -iirfui-i' r> Ini-mn-.'ll} <li'si-rihi'il ;i- piinrtiiti'. 



