219 



Measuremen ts. — Original specimen 

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

 line, 9 mm. 



The original specimen comes from the 

 Livonia Salt Shaft (Hamilton shales). 

 Specimens showing the pits, but other- fig. m Ambocceiia 



spinoxa. Brachial valve 



wise not differing much from A. umhoiinta, of t he tv P e specimen, 



° ' much enlarged (alter 



have been found at Eighteen Mile Creek, ciarke). 

 and are referred to this species. They were found in the 

 following positions: Moscow shales, two feet below Stylio- 

 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. 1893: Pal. N. Y., 



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



Shells Spirifer-like ; usually small; valves very unequal; 

 pedicle valve elevated, with a high cardinal area, the del- 

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

 del tidium, which is perforated below the apex. Surface 

 plicate. Dental lamellae strong, converging rapidly, and 

 meeting a, median septum. Cardinal process a double 

 apophysis. Brachidium an extroverted spire. 



Cyrtina hamiltonensis. Hall. (Fig. 129.) (Pal. N. Y '., 

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



Distinguishing Characters. — Small size; pyramidal char- 

 acter of pedicle valve ; slightly convex brachial valve; high, 



^3- ^'TC.- 







Fig. 129. Cyrtina hamiltonensis. Dorsal, ventral, cardinal, and profile views (from 

 Hall). 



triangular, commonly arcuate, area; incurved, frequently 

 distorted, beak; strong mesial sinus; broad fold; six to 

 eight plications on each side of fold and sinus. 



