219 



Measureinen ts.— () r i jl;' i ii ;i 1 s p e c i ni e n 

 (Clarke): length. 7 mm.: width on the hinge 

 line, 9 mm. 



The original sj)ec'imen comes from the 

 Livonia Salt Shaft (Hamilton shales). 

 Specimens showing the pits, but other- fig. iss Amhoa.iia 



J^ o I ' spinosa. Brachial valve 



wise not differing mneh from .4. umhomita, ^*J^ e^^PiTg^irtaft",- 

 have been found at Eighteen Mile ("reek, ciarke). 

 and are referred to this s])eeies. They were found in tlie 

 following positions: Moscow shales, two feet below St.vlio- 

 lina band, at Section 3 ; Hamilton shales, nine to twenty- 

 five feet below the Encrinal limestone, at Section 7. 



Genus CYRTINA. Davidson. 



[Ety. : Kyrtia, a fishing basket.] 



(1858: Monogr. British Carbonif. Brachiopoda, p. 66. 1898: Pal. N. Y., 

 Vol. VIII., Pt. II., p. 43.) 



Shells Spirifer-hke ; usually small: valves \Qi'\ unequal: 

 })edicle valve elevated, with a high cardinal area, the del- 

 thyrium of which is covered by an elongate, convex pseudo- 

 deltidium, which is perforated below the apex. Sui-face 

 plicate. Dental lamelke strong, converging rapidly, and 

 meeting a median septum. Cai'dinal process a double 

 apophysis. Brachidium an extroverted spire. 



Cyrtina HAMiLTONKNsis. Hall. ( Fig. 129. ) (Pal. X. v., 

 Vol. IV., p. 268, Pis. XXVn., XLIV.) 



Distinguishing Clmraetei-s.— '^m;\\\ size; pyramidal cliar- 

 acter of pedicle valve ; slightly convex In-achial valve: high, 



Fig. 129. Cyrtina hamilfont-nsis. Dorsal, ventral, cardinal, and profile views (from 

 Hall). 



triangular, commonly arcuate, area; incurved, frecpiently 

 distorted, beak; strong mesial sinus; bi-oad fold; six to 

 eight plications on each side of fold and sinus. 



