PLATE 29. 
Legend. D. Deltarium. (s')T. Syringoid tube. 
F, Foramen. j. Cardinal process. 
s'. Rostral callous. c. Urura, 
d. Dental lamellee. b. Dental sockets. 
A. Delthyrium. a. Adductor scars. 
A. Cardinal area. r. Diductor scars. © 
s. Median septum. 
SPIRIFER, Sowxrsy. 
(GLABRATI.) 
Page 758. 
Sprrirer mata, Billings. 
Fig. 1. Dorsal view of an exfoliated shell. 
Fig. 2. Another individual with more pronounced median fold; showing the 
A smooth exterior. 
Corniferous limestone. Ohio. 
SPIRIFER suBuMBOoNA, Hall. 
Fig. 3. Ventral view of a preparation; showing the smooth exterior and the 
form of the spiral. x 3. 
Limestone of the Marcellus epoch. Stafford, N. Y. 
CYRTIA, Datman. 
Page 159. 
Cyrria ExporRECTA, Wahlenberg. 
Fig. 4, The exterior of anormal example. (DavVIDSON.) 
Fig. 5. Transverse section of the umbonal region of the pedicle-valve; show- 
ing the dental lamellz resting on the bottom of the valve and the 
thickening at their union with the deltarium. 
Wenlock limestone. England. 
Cyrtia exporrecta, Wahlenberg, var. arrEcTA, Hall and Whitfield . 
Figs. 6, 7. Cardinal and profile views of the original specimen. 
Niagara group. Louisville, Kentucky. 
CyrtiA RADIANS, Hall. 
Figs. 8, 9. Cardinal and front views; showing the finely lineate exterior. 
Clinton group. Rochester, N. Y. . ‘ 
Cyrtia ara, Hall. 
Fig. 10. A front view of an internal cast of the pedicle-valve; showing the 
muscular area and the faintly plicated sinus. 
Fig. 11. A cardinal view of a similar internal cast; showing the depression 
left by the internal thickening of the deltarium. 
Chemung group. Meadville, Pennsylvania. 
210 
