﻿1040 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I27 



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 other brachial valve showing the median septum and muscle scars, X 3> para- 

 type, 116815c; (50, 51) interior and exterior of a small brachial valve, X 3> 

 paratype, n6Si5i; (46, 52) side and interior views of a nearly perfect brachial 

 valve, X 3, paratype, 116815J ; (53) interior of a large but fragmentary brachial 

 valve showing elaborately developed pallial marks, X 3, paratype, 116815k; 

 (54, 55) interiors of fragmentary brachial valves showing details of the muscle 

 scars and pallial marks, X 4, paratypes, 116815I1 and 116815-I; (56, 57) interior 

 and exterior of a large brachial valve, X 3, showing muscle scars, paratype, 

 116815m. 

 Horizon and locality same as preceding. 



D. Conotreta gigantea Cooper, new species 251 



(58) Under side of posterior of a large pedicle valve, X 2, showing part of pedicle 

 groove and elongate muscle tracks, paratype, 117968a. 



Horizon and locality same as preceding. 



E. Conotreta gigantea Cooper, new species 251 



(59) Interior of a brachial valve showing low median septum and muscle scars, 

 X 3, paratype, 117968b; (60) posterior of another but imperfect brachial valve 

 showing triangular pit and muscle scars, X 3, paratype, 1 17968c. 



Horizon and locality same as preceding. 



Plate 18 



ACANTHAMBONIA, CONOTRETA, PATERULA, RhYSOTRETA, ScAPHELASMA, SpONDYLOTRETA, 



TORYNELASMA, UnMFERINA 



A. Spondylotreta concentrica Cooper, new species 255 



(1, 2) Exterior and interior of the brachial valve, X 6, paratype, 116826c; (3-6) 

 respectively side, posterior, apical, and interior views of the pedicle valve, X 4, 

 holotype, 116826a; (7) interior of another pedicle valve showing the spondylium- 

 like apical structure, ca X 10, paratype, 116826b. 



Pratt Ferry formation (lower 3 feet), 0.2 mile southeast of Pratt Ferry, 

 Blocton (15') Quadrangle, Ala. 



B. Undiferina rugosa Cooper, new species 263 



(8, 9) Exterior and interior of the brachial valve, X 4, paratype, 116832a; (20) 

 interior of the same specimen, X 6, showing apical structure and median sep- 

 tum; (10, 11) posterior and exterior views of another brachial valve, X 4> holo- 

 type, 116832b; (12, 13) interior of holotype, X 4 and X 8, showing expanded tip 

 of median septum; (15) exterior of the holotype, X 8, showing the strongly 

 wrinkled surface; (14) interior of a brachial valve tilted slightly to show the 

 median septum and its expansion in partial profile, X 8, paratype, 116832c; (18) 

 same specimen in normal interior view, X 4', (16) same as preceding in exterior 

 view, X 6, to show the wrinkled surface; (17) imperfect brachial valve with no 

 expansion of the septum, X 6, paratype, n6832d; (19, 21) imperfect brachial 

 valves showing an expanded and a tubular end on the median septum, X 6, 

 paratypes, 116832c and n6832f. 



Horizon and locality same as preceding. 



C. Conotreta ? concentrica Cooper, new species 250 



(22) Apical view of an imperfect pedicle valve, X 4, showing the minute foramen, 

 holotype, 11 68 14. 



Horizon and locality same as preceding. 



D. Acanthambonia minutissima Cooper, new species 212 



(23) Interior of the brachial valve showing the apical structure, X 10, paratype, 

 116795a; (25) posterior part of the same specimen, X 15, showing the broad 

 apical plate; (24) interior of the pedicle valve showing delthyrium, X 10, holo- 



