Group I.—Valves concavo-convex.] 
BRACHIOPODA. aA. 355 
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 sufticiently 
understood by the writers for positive classification. 
Rnnnnnnnnnnnnn mw 
RRARRARRHK 
1838. 
1843. 
1844, 
1847. 
1856. 
1859. 
1863. 
1883. 
1892. 
Group I.—Valves concavo-convex. 
. tncurvata Shepard, Trenton. 
. thalia Billings, Trenton. 
trentonensis, n. sp., Trenton. 
septata W. and S., Trenton. 
neglecta James, Hudson River. 
naglecta, var. acuta, n. var., Hudson River. 
vetusta James, Hudson River. 
rugosa Rafinesque (de Blainville), Hudson River. 
rugosa, var. subtenta Conrad, Hudson River. 
planoconvexa Hall, Hudson River. 
planodorsata W. and S., Hudson River. 
wisconsinensis Whitfield, Hudson River. 
trilobata Owen, Galena. 
. fluctuosa Billings, Hudson River. 
. nutans (James Ms.) Meek, Hudson River. 
. hecuba Billings, Hudson River. 
Group II.—Valves biconvex. 
. minor Walcott, Upper Pogonip. 
. scofieldi W. and S., Galena Shales. 
. billingsi, u. sp., Trenton and Galena. 
. emaciata W.and S., Galena. 
- halliana Miller, Lower Hudson River. 
. sinuata (James Ms.) Meek, Hudson River. 
. suleata de Verneuil, Hudson River. 
. eardinalis Whitfield, Hudson River. 
STROPHOMENA INCURVATA Shepard, sp. 
PLATE XXX, FIGS. 36—40, 
Producta incurvata SHEPARD. American Journal of Science, vol. xxxiv, p. 144, figs. 1, 2. 
Orthis incurvata CASTELNAU. Wssai sur le Syst?me Silurien de l’Amérique Septentrionale, 
p. 38. 
Strophomena convera OWEN. Geological Exploration of lowa, Wisconsin and Illinois, p. 70, 
pl. xvu, fig. 2. 
Leptena filitexta HALL. Paleontology of New York, vol. i, p. 111, pl. xxx1B, figs. 3a to 3f. 
Strophomena filitexta BILLINGS. Canadian Naturalist and Geologist, vol. i, p. 203, figs. 1, 2. 
Strophomena filitexcta HALL. Twelfth Report N, Y. State Cabinet of Natural History, p. 70. 
Strophomena filitexta BILLINGS. Geology of Canada, p. 164, fig. 142. 
Streptorhynchus filitexta HALL. Second Annual Report New York State Geologist, pl. Xx x1x, 
figs 1-7; pl. xu, figs. 11-14 (not figs. 10 and 15=S. neglecta James) 
Strophomena jfilitexta HALL. Palxontology of New York, vol. viii, pt.i, p. 251, pl. rx, figs. 1-17; 
pl. 1xA, figs. 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— 
