BRACHIOPODA. 340 
Lingula ioweiisis.] 
Dorsal valve strongly convex, both transversely and longitudinally. In the 
interior of this valve, the cardinal margin is broadly flattened, striated, and divided 
centrally by a well defined, narrow depression, which terminates at a point one-fourth 
the length of the shell from the posterior edge. Near the posterior end of this 
depression are faint traces of the urabonal scar. The vascular trunks are discernible 
on each side and anterior to the rostral depression, and having the same curve as 
the outer margin of the valve, thence proceed to a point somewhat beyond the pos- 
terior half of the shell, where they gradually converge and meet near the anterior 
margin. Vascular branches originate only from the outer side of the vascular 
trunks. The enclosed space seems to represent the tracks of the anterior and 
central muscular scars. 
The outline of this species and the convexity of the dorsal valve are variable. 
The broadly subtriangular specimens have more strongly convex dorsal valves than 
the narrow and less triangular form. There is no other species of Lingiila from 
Lower Silurian strata having the peculiarly deflected anterior portion of the shell 
so characteristic of this species. Lingiila linguata Hall* from the Clinton group is 
the only other American species with this peculiarity, and differs from L. defleda in 
having parallel lateral margins. 
Formation and locality— From the shales near the base of the Galena group on the farm of Ole 
Hansen, near Fountain, and in the Hudson River group near Spring Valley, Minnesota. 
Collectors.— F. O. Ulrlch and C. Schuchert. 
Mus. Reg. Nos. 7675, 7676. 
LiNGULA lOWENSis Oicen. 
PLATE XXIX, FIGS. 10-22. 
1844. Lingula iowensis Owen. Geol. Rep. Iowa, Wisconsin and Illinois, p. 70, pi. xv, flg. 1. 
1851. Lingula quadrata? Owen (not Eich.). Geological Report of Wisconsin, Iowa and Minnesota, 
pi. iiB, flg. 8. 
1862. Lingula quadrata Hall. Geology of Wisconsin, vol. i, p. 46, flg. 1, and p. 435. 
1868. Lingula gwadraia Meek and WouTnEN. Geological Survey of Illinois, vol. iii, p. 305, pi. ii, flg. 4. 
1882. Lingulella iowensis Whitfield. Geology of Wisconsin, vol. iv, p. 242, pi. ix, flg. 1. 
1892. Lingula iowensis Hall. PaUuontology of New York, vol. viii, part 1, p. 8, pi. i, flg. 14. 
Original description: "Resembles L. lamellaia H., of the Niagara group, 
but is larger and straighter on the lateral edges. It differs from L. rectilateris 
[probably meant L. rectilateralis Emmons], in being flatter and not so pointed at 
the apex." 
From the figure given by Owen, we cannot be positive in the identification of 
this species, but since comparison is made with L. rectilateralis Emmons, in the 
*l'al. New York, vol. viii. p. 17:!, pi. ivK. fig. 5; W)2. 
