474 , THE PALEONTOLOGY OF MINNESOTA. 
[Ualiuu niculleti. 
Hallina nicolleti, n. sp. 
PLATE XXXI V^ FIGS. 59-62. 
1892, April 1. Hallina nicolleti W. and S. American Geologist, vol. ix, p. 293. 
1892, April 9. Zygospira aquila Sardeson. Bulletin of the Minnesota Academy of Natural Sciences, 
vol. iii, p. 335, pi. iv, figs. 15-18. 
* Shell small, rostrate, biconvex, oval or subcircular in outline. Ventral valve 
convex, iDoint of greatest elevation about mid-length, with a shallow, vety nai^row 
sulcus down the center, bordered on each side with a low, rounded ridge, which 
becomes more prominent toward the anterior margin. The antero-lateral limits of 
the shell may be smooth or with as many as five low, rounded plications or marginal 
undulations. Beak strongly incurved, with a small, oval pedicle opening bounded 
by rudimentary deltidial plates on each side. Dorsal valve evenly convex and 
trilobed toward the anterior edge; in some specimens the lateral lobes may have 
as many as six low, rounded plications along the front margin. Calcified brachial 
supports much as in Hallina sqfordi, except that the outer bands are curved later- 
ally, while the anterior recurved portion is shorter. Articulating processes and 
muscular scars unknown. 
Hallina nicolleti is easily distingushed from associated species, on account of its 
small size and camarelloid exterior. It differs from Hallina safordi in its fold and 
sinus, and the usually obsolete marginal plications. Its associated species are the 
same as occur with H. saffordi. 
Named for Jean N. Nicollet, geologist and geographer of the Northwest. 
Formation and locality.— Abundant in the upper third of the Trenton limestone at Minneapolis, 
St. Charles, Rochester and Fountain, Minnesota; Decorah, Iowa, and in the "Lower Blue beds" at Beloit, 
Wisconsin. 
Collectors.— B. O. Ulrich, W. H. Scofield and the writers. 
Mus. Reg. Nos. 339, 434, 436, 438, 440, 652, 660, 8238, 8239. 
