PLATE XXVII. 



(Figures 1-17 by E Emmons; 18 by F. B. Meek; 19, 20 by U. P. Wiiitkield.) 



Legend : D. Deltidium. d. Dental plati^a. 



s'. 'i'l'jmsverse delthyrial plate. a.~Addnctor scars. 



T. Tubular jiortion of plate. r. Diducfcor scars. 



Genus SYRINGOTHYRIS, A. Winchell. 



Page 47. 



Syringothyris typa, a. WiiK-!ull. 



See Plate 26. 



Fig-s. 1, 2. Cardinal and ventral views of one of the original specimens ; showing the normal form of the 



species. 

 Fig. e!. A portion of the umlional region of the pedicle-valve ; showing the dental plates and tubular 

 transverse plate. 



Burlington limestone. 



Syringothyris texta, Hall. 



See Plate 26. 

 Fig. 4. The exterior of a large brachial valve ; showing the prevailing extended form of the shell. 

 Fig. 5. An internal cast of the pedicle-valve ; showing the impres.sionsof the adductor and diductor scars. 

 Fig. 6. The cai-dinal view of a specimen retaining both valves, and showing the usual elevation of the area. 

 Fig. 7. The central cardinal portion of the pedicle-valve ; showing the transverse delthyrial plate 



and the free, completed extremity of the tube which is elsewhere adherent to the inner surface 



of the plate. X 2. 

 Fig. 8. A transverse section of the pedicle-valve a .short distance below the apex ; showing the dental 



lamellte resting on the bottom of the valve, the transverse plate and the adherent tube on the 



inner side. 

 Fig. 9. A section of the same valve nearer the hinge and below the edge of the transverse plate. The 



free poi'tion of the tube is seen to be open on the inner side. 

 Fig. 10. A longitudinal axial section of conjoined valves ; showing the extent of the internal tubular plate. 



The portion marked s' is the deltidial covering and is represented incorrectly, as it extends for 



only about two-thirds of the distance from the apex to the cardinal process of the brachial 



valve. 

 Fig. 11. A transverse section ; showing the formand extent of the spiral cones. 

 Fig. 12. An enlargement of the shell-structure ; showing the minute, distant pores scattered among the 



fibers. 



Keokuk group. Neio Promdence, hidiana. 



Syringothyris Randalli, Simpson. 



Fig. 13. A cardinal view of an internal cast ; showing the position of the deltidial covering, and the tubular 

 extension of the apical plate. 



Fig. 14. An internal cast of the pedicle-valve ; showing the adductor and diiluctor scars. 



Fig. 15. A cardinal view of a specimen retaining the convex deltidial covering. 



Fig. 17. A cardinal view of the specimen represented in fig. 14 ; showing the position of the deltidial cov- 

 ering and of the internal split tube. 



Fig. 16. A similar view of another specimen, in which the cast of the tubular plate is concealed by the 

 upward projection of the filling of the delthyrial cavity. The position of the deltidial covering 

 is not defined with sufficient distinctness in the figure. 

 Waverly grouj). Warren, Penn. 



