790 THE PALEONTOLOGY OF MINNESOTA. 



LOrthoceras juneeum. 



thin, gently arched, distant from one-fourth to one-twelfth the diameter; siphuncle 

 a cylindrical ventral tube; outer chamber very deep." (Hall, loc. cit.) 



This species appears to be represented by various imperfect examples of some- 

 what smaller size than the New York specimens, but otherwise agreeing with the 

 above description and the original figures. 



Formation and locality. Not uncommon in the Trenton limestone at Minneapolis; in the Trenton 

 shales at St. Paul, Eyota, Lanesboro and Fountain, and the Galena limestone at Rockdell. Minnesota. 

 In the lower blue beds of the Trenton at Mineral' Point, Wisconsin, and in the upper buff beds at Rock- 

 ton, Illinois. Also common in the Birdseye limestone at Watertown and elsewhere, New York. 



Museum Register, Nos. 721, 4049, 4052, 5045, 51 12, 5578, 7927, 8276, 8277, 8278. 



ORTHOOERAS JUNCEUM Hall, 1847. 



Orthoceras juneeum HALL, 1847. Pala'ontology of New York, vol. i, p. 204, pi. XLVII, flgs. 3a-/. 



To this species -are referred a few internal casts of small shells, with circular 

 cross-section, central sipho, regular and equidistant septa. The original description 

 of the species is as follows: "Slender, terete-cylindrical, tapering very "gradually; 

 septa thin, distant from one-fourth to one-third the diameter; siphuncle small, 

 central, section circular; surface finely striated transversely, but without longitu- 

 dinal striae." 



Formation and locality. In the Trenton shales at Minneapolis and near Fountain, Minnesota. In 

 the lower blue beds at Janesville, Wisconsin. 



Museum Register, Nos. 7 1C, 8280, 8281, 8282. 



ORTHOCERAS compare AMPLICAMERATUM Hall, 1847. 



PLATE XLVII, FIO. Ifl. , 



Of. Orthoceras amplicameratum HALL, 1847. Pala-ontology of New York, vol. i, p. 205, pi. LI, flgs. la-p>. 



There are a few moderately large fragments of orthoceran casts which present 

 an agreement with this species in general aspect and depth of the air-chambers. In 

 the original description, based on much more complete examples than are here 

 afforded, the species is thus characterized: "Teretely cylindrical, extremely 

 elongated, very gradually tapering; outer chamber profound; septa distant about 

 one- third the diameter, very conve, siphuncle ex centric, small; surface ?; section 

 circular." 



In one of our specimens the external surface appears to have borne fine, equi- 

 distant, longitudinal striae. 



Formation and locality. From near the base of the Galena limestone at Preston, Minnesota; in the 

 lower blue beds of the Trenton at Mineral I'nim, Wisconsin. 



Museum Register, Nos. 8285, 8280, 8287. 



