PLATE XII. 



(FiRUies 1-5, S-Jl Ijy K. f WHiiHELu, i>, 7 by F. B. Meek.) 



Leg-end. H. Hing-e-liiic. b. Dental sockets. 



ID. Deltidiuni, pedicle-valve. t. Teeth. 



C. Deltidiuni, brachial valve. a. Antericir adductors. 



a. Cardinal area, outer jiortioii. a'. Posterior adductor.'*, 



j. Cardinal pi'oces-s. r. Diiluctors. 



i. Lobes of cardinal (irncess. 



Genus STROPHONELLA, Hall. 



Papre 29U. 



StROPHONELLA ( ) STRIATA, Hixll. 



Fig. 1. The exterior of a brachial valve. 



Fig-. 2. The interior of a j)edicle-valve ; showing the extension of the dental laraellffi along the sides of 



the musoiilar area, and the crenulations of the cardinal margin near the delthyrium. 

 Fig. 3. An enlargement of the central portion of the brachial valve ; showing the cardinal area, its 

 crenulated margin, and the deltidiuni envelojiing the lower portion of tlie lolies of the cardinal 

 process. In this drawing the specimen is viewed with tlie cardinal area nearly at right angles 

 to the line of \ision ; the groove between the lobes of the cardinal process is, therefore, much 

 foreshortened, and made to appear shallow ; the cruial Hdges are also to be regarded as I'e- 

 ti'eating rapidly into the background. 



Niagara group. lValdro7i., Indiana. 



Stropiionella semifasciata, Hall. 



Fig. 4. The exteiior of the concave pedicle-valve. 



Fig. 5. An enlargement of the central portion of the area of both valves ; showing the development of 



the deltidia and the obliipie striaj on the broad triangular .sjiace enclosed by tlie lines o, a. a. 



[This space should be iletined by lines extending from the apex to the limit of the figure on 



each side, and which may be obscure in some of the figures.] 

 Niagara gron]i. WaUlron. hidiana. 



StROPHONELLA Leavenworthana, Hall. 



Fig. 6. The exterioi' of a brachial valve. 



Fig. 7. A profile of the same ; showing the concavity in eai-ly growth-stages, foUoweil by great convexity 

 and strong geniculation. 



Fig. 8. The interioi- of the brachial valve ; showing the crenulations of the cai-dinal margin, the cardinal 

 process, slightly develojied crural plates, and the .adductor impressions. 



Fig. 9. The interior of the pedicle-valve ; .showing the crenulations of the hinge-margin, tlie closed del- 

 thyrium, and the arrangement of the muscular scars. 



Lower Helilerberg group. Albany county^ N. Y. 



StROPHONELLA punctulifera, Coiirad. 



Fig. 10. The exterior of the brachial valve; showing tlie concavity in the umbonal, and convexity in the 

 pallial region. 



Fig. 11. An internal cast of a brachial valve; showing the muscular imprints ,ind the crenulations in the 

 matrix left by the removal of the hinge. 



Fig. 12. The cardinal areas of both valves of fig. 10 ; showing the narrow convex deltidiuni closing the 

 delthyi-iuni in each valve. X 1^. 



Lower Helderlierg group. Near ClarJrsvUle, N. T. 



StROPHONELLA AMPLA, Htlll. 



Fig. 13. An internal cast of a pedicle-valve; showing the muscular impressions and marks of the strongly 

 pustulose interior surface. In the imprint left by the cardinal area are seen the crenulations 

 of the hinge-line, and the mark of the .small, linear convex deltidium. 

 Scthoharie grit. Albany munty, N. Y. 



Fig. 14. The interior of a pedicle-valve in which external evidence of the deltidiuni is lost and the crenula- 

 tions of the hinge extend more than half the length of the area. The margin of the area on 

 each side of the deltidium has been broken away by the detachment of the cardinal )iroi;e.ss of 

 the other valve. 



Corniferous limestone. Owmdaga VaUry, N. Y. 



Fig. l.'i. An enlargement of the surface sfriie. 



