360 THE PALEONTOLOGY OF MINNESOTA. 



[Llngalelllde. 



Family LINGULELLID.E, Schuchert, 

 LEPTOBOLUS OCCIDENTALIS Hall, 



1871. Leptobolus occidentalis HALL. Description n. sp. Foss. from the Hudson River group, p. 3, 



pi. in, flg. 18. 



1872. Leptobolus occidentalis HALL. Twenty-fourth Report N. Y. State Cab. Nat. Hist., p. 227. 



pi. vn, flg. 18. 

 1892. Leptobolus occidentalis HALL. Pal. N. Y., vol. viii, pt. i, pi. in, flg. 7. 



This species will probably be found in the lower portion of the Hudson River 

 group of Minnesota, since it occurs in abundance in Iowa and Wisconsin. Mr. E. 0. 

 Ulrich has collected one specimen which may prove to belong to this species, but 

 its position is such as to leave its identity in doubt. 



Formation and locality. In the lower portion of the Hudson River group at Hawley's mills or Graf, 

 Iowa; Plattville and Clifton, Wisconsin; Ottawa, Canada (Ami). The specimen from Minnesota was found 

 three miles north of Spring Valley. 



Genus. SCHIZAMBON, Walcott. 



1884. Schizambon, WALCOTT. Monograph U. S. Geological Survey, vol. viii, p. 69. 

 1887. Schizambonia, (EHLEBT. Manuel de Conchyliologie, Fischer's, p. 1266. 

 1892. Schizambon, HALL. Palaeontology of New York, vol. viii, pt. i, p. 113. 



Original description: "Shell ovate or oblong-oval, inequivalve; valves inarticu- 

 late; larger or ventral valve most convex, with a short obtuse beak at the cardinal 

 margin. Foramen oblong and opening on the summit of the valve ; no area nor 

 deltidium; cardinal edge thin; smaller or dorsal valve nearly as convex as the larger, 

 slightly flattened along the median line. 



"Structure calcareo-corneous, consisting of a nacreous outer layer with a closely 

 attached inner calcareous layer. Both layers are thought to be punctured by scat- 

 tering spines apparently on the outer edges of the laminae or lines of growth. 



"The interior of the larger valve shows the oblong foramen in a slight elongate 

 depression and a pair of muscular scars just in front of it on each side of a slight 

 longitudinal depression; from near the beak on each side of the foramen, a shallow 

 sharply defined depression extends obliquely outward. No other markings were 

 observed. In the interior of the dorsal valve a pair of anterior central muscular 

 scars terminate their path of advance from the beak, a slight rounded ridge rising 

 on the central line; posterior to these a large pair occur, and still beyond and more 

 posterior a third pair, a narrow rounded edge extending obliquely down from the 

 beak on each side between the central and lateral scars." 



Type Schizambon typicalis Walcott. 



Since the interior characters are unknown in Schizambon ? dodgii, n. sp., and 

 6". ? lockii. n. sp., these forms are placed in this genus provisionally. S. typicalis is 



