Group I.— Valves concavo-convex.] 
BRACHIOPODA. 
385 
allows any of the species mentioned below being referred to either one of the 
groups. There are, besides these species, a few others, but they are not sufficiently 
understood by the writers for positive classification. 
* 
Group I. — Valves concavo-convex. 
S. iacurvuta Shepard, Trenton. 
S. thalia Billings, Trenton. 
S. trentonensis, n. sp., Trenton. 
S. septata W. and S., Trenton. 
S. neglecta James, Hudson River. 
8. naglecta, var. acuta, n. var., Hudson River. 
S. vetusta James, Hudson River. 
S. rugosa Raflnesque (de Blainville), Hudson River. 
S. rugosa, var. subtenta Conrad, Hudson River. 
<S. planoconvexa Hall, Hudson River. 
planodorsata W. and S., Hudson River. 
S. wisconsinensis Whitfield, Hudson River. 
S. trilobata Owen, Galena. 
S. fluctuosa Billings, Hudson River. 
S. nutans (James Ms.) Meek, Hudson River. 
S. hecuba Billings, Hudson River. 
GrROUP II. — Valves biconvex. 
? S. minor Walcott, Upper Pogonip. 
S. scofieldi W. and S., Galena Shales. 
S. billingsi, n. sp., Trenton and Galena. 
8. emaeiata W. and S., Galena. 
S. halliana Miller, Lower Hudson River. 
S. sinuata (James Ms.) Meek, Hudson River. 
S. sulcata de Verneuil, Hudson River. 
S. cardinalis Whitfield, Hudson River. 
Strophomena incurvata Shepard, sp. 
PLATE XXX, FIGS. 3(5—40. 
1838. Producta incurvata Shepard. American Journal of Science, vol. xxxiv, p. 144, figs. 1, 2. 
1843. Orthis incurvata Castelnau. Essai sur le Syst&me Silurien de I'Am^rique Septentrionale, 
p. 38. 
1844. Strophomena convexa Owen. Geological Exploration of Iowa, Wisconsin and Illinois, p. 70, 
pi. XVII, flg. 2. 
1847. Leptcena filitexta Hall. Pala?ontology of New York, vol. i, p. Ill, pi. xxxiB, flgs. 3a to 3f. 
1856. Strophomena filitexta BtLLiNGS. Canadian Naturalist and Geologist, vol. i, p. 203, figs. 1, 2. 
1859. Strophomena filitexta Hall. Twelfth Report N. Y. State Cabinet of Natural History, p. 70. 
1863. Strophomena filitexta Billings. Geology of Canada, p. 164, flg. 142. 
1883. Streptorhynchus filitexta HALL. Second Annual Report New York State Geologist, pi. xxxix, 
flgs 1-7; pi. XLii, flgs. 11-14 (not flgs. 10 and 15=S. neglecta James) 
1892. Strophomena filitexta HALL. Pala3ontology of New York, vol. viii, pt. i, p. 251, pi. ix, flgs. 1-17: 
pi. ixA, flgs. 11-14. 
Original description: "The extent of the magnesian limestone in Wisconsin, 
Upper Illinois and Missouri, struck me with surprise. I observed it, in addition to 
the country already noticed between Chicago and Ottawa, as the prevailing forma- 
tion about the northern extremity of Michigan, the islands about Michillimacinac, 
25- 
