PLATE XXVI. 
(Figures 1-7, 9-11 by B. P. Whitfield; 8 by F. B. Meek; 12 by E. Emmons.) 
Legend : 
A. Cardinal area. 
A. Deltliyrium. 
Dg. Deltidial grooves, 
s^. Transver.se delthyrial plate. 
T. Tubular portion of jilate. 
T^. Internal cast of tube, 
j. Cardinal process, 
b. Dental sockets, 
r. Diductor scars, 
a. Adductor scars. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Genus CYKTIA, Dalman. 
Page 40. 
CyRTIA ALTA, Hull. 
1. The internal cast of the brachial valve; showing the striated cardinal area, structure of the artic¬ 
ulating apparatus and the faint plications on the median fold. 
2. The front view of an internal cast of the pedicle-valve; showing the muscular area and the faintly 
plicated sinus. 
3. An exterior view of the cardinal area of the pedicle valve ; showing the concave plate tilling the 
upper jiart of the delthyrium. 
4. A cardinal view of an internal cast of the pedicle-valve; showing the impression left by the 
thickened inner wall of the delthyrial plate. 
5. A xiortion of an internal cast of a small brachial valve retaining traces of the muscular scars. 
Chemung grouji. Meadville, Penn. 
Genus SYEINGOTHYRIS, A. Winchell. 
Page 47. 
Syringotiiyris typa, a. Winchel]. 
Fig. 
Fig. 
Fig. 
6. The apical portion of a jicdicle-valve ; showing the dental plates, the delthyrial plate, with the 
central tubular portion jirojecting beyond its broken margin. 
7. The opposite side of the same sjiecimen ; showing the extension of the canaliferous tube which is 
slit along its inner surface. 
10. The interior of the umbonal portion of the pedicle-valve; showing the greatly thickened tubulai- 
or canaliferous plate, not closed along its inner surface. 
Burlington limestone. Burlington, Iowa. 
Syringothyris subcuspidatus, Hall. 
Fig. 8. A cardinal view of the original specimen. 
Keokuk limestone. Keokuk, Iowa. 
Fio-. 11. The interior of a large jiedicle-valve ; showing the transverse plate and the extension of the tube. 
Keokuk grou^). Nauvoo, Illinois. 
Syringothyris texta, Hall. 
Fig. 9. Central cardinal portion of an internal ’cast of the conjoined valves ; showing the impressions of 
the cardinal xirocess, dental jilates and the filling of the tulmlar jiortion of the transverse plate. 
Fig. 12. A jirejiaration, showing the elongate ejiiral brachial supjiorts, the jugal pi-ocesses and a portion 
of the crura, (c.) 
Keokuk group. New Providence, Indiana. 
