BRACHIOPODA. 385 



Group I. Valves concavo-convex.] 



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. incurvata Shepard, Trenton. 



S. thalia Billings, Trenton. 



S. trentonensis, n. sp., Trenton. 



S. septata W. and S., Trenton. 



S. neglecta James, Hudson Eiver. 



S. naglecta, var. acutn, n. var., Hudson River. 



S. vetusta James, Hudson Kiver. 



S. rugosa Raflnesque (de Blainville), Hudson River. 



S. rugosa, var. subtenta Conrad, Hudson River. 



S. planoconvexa Hall, Hudson River. 



S. planodorsata W. and S., Hudson River. 



S. wiseonsinensis Whitfleld, Hudson River. 



S. trilobata Owen, Galena. 



S. fluctuosa Billings, Hudson River. 



S. nutans (James Ms.) Meek, Hudson River. 



S. hecuba Billings, Hudson River. 



GROUP II. Valves biconvex. 



f S. minor Walcott, Upper Pogonip. 

 S. scofieldi W. and S., Galena Shales. 

 S. billingsi, n. sp., Trenton and Galena. 

 8. emaciata W. and S., Galena. 

 S. halliana Miller, Lower Hudson River. 

 S. sinuata (James Ms.) Meek, Hudson River. 

 S. suleata de Verneuil, Hudson River. 

 S. cardinalis Whitfleld, Hudson River. 



STROPHOMENA INCURVATA Shepard, sp. 



PLATE XXX. FIGS. 38-40. 



1838. Producta incurvata SHEPARD. American Journal of Science, vol. xxxiv, p. 144, figs. 1, 2. 



1843. Qfthis incurvata CASTELNAU. Essai sur le Syst^me Silurien de l'Am<5rique Septentrionale, 



p. 38. 



1844. Strophomena convexa OWEN. Geological Exploration of Iowa, Wisconsin and Illinois, p. 70, 



pi. xvii, flg. 2. 



1817. Leptcena filitexta HALL. Palaeontology of New York, vol. i, p. Ill, pi. xxxiB, flgs. 3a to 3f. 

 1856. Strophomena filitexta BILLINGS. Canadian Naturalist and Geologist, vol. i, p. 203, flgs. 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=5'. neglecta James) 

 1892. Strophomena filitexta HALL. Palaeontology 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- 



