Geabau — Faux as of the Hamilton Group. 



269 



lowest part of the Moscow shales, but reappears suddenly between three and 

 five feet above the Encrinal limestone. After that it does not appear again in 

 these shales. 



93. Stropheodoxta (Pholidostkophia) xacrea, Hall. 



1867, Hall, Pal. N. Y., vol. 4, p. 104, pi. 18. 



1892, J. Hall and J. M. Clarke, Pal. N. Y., vol. 8, pt. 1, p. 284. 



This little species is most characteristic of the lower Trilobite bed, where 

 it occurs in considerable number and perfection. It is rare below these beds, 

 onlv a few specimens having been obtained, but is not known in or below the 

 Strophalosia bed. Above the Trilobite beds it is found only in the Jlodio 

 morpha subalata bed and in the Encrinal limestone, where it suddenly reap, 

 pears in considerable quantity. It then disappears from this region. 



94. Stropheodoxta (Leptostrophia) juxia, Hall. 

 1867, Hall, (S. textili.s), Pal. N. Y., vol. 4, p. 108, pi. 18. 

 1892, J. Hall, and J. M. Clarke, Pal. N. Y., vol. 8, pt. 1, p. 284, pi. 15. 

 A few fragmentary specimens of this species were found in the S. demissa 



bed. 



95. Stropheodoxta plicata, Hall. 

 1867, Hall, Pal. X Y., vol. 4, p. 114, pi. 63. 

 (See also vol. 8.) 



This species was first described from Iowa City, and subsequently from 

 Independence, Iowa. In the S. demissa bed occur several small Strophe- 

 odontas with coarse, rather angular plications, and unlike any other form in 

 the Hamilton of Xew York. I refer them to this species, for though the 

 plications are more angular than those of the type specimen, the difference 

 appears not to be sufficient fur specific distinction. A well marked pedicle- 

 valve has about thirteen plications near the beak, while near the front the 

 number is nearly twice that, from intercalation. A stronger plication marks 

 the centre of the valve. The area is narrow, linear, somewhat concave, and 

 vertically striated, the margins strongly crenulated. "The cardinal process 

 of the brachial valve is strongly bilobed, the area linear, and the interior 

 surface minutely pustulose. 



A small brachial valve measures 11 mm. in width, by 8 mm. in height. In 

 one specimen, apparently of this species, the cardinal angles are produced into 

 mucronate extensions. 



