PLATE XL 
Figs. 1-llb. DIELASMA SUBSPATULATUM Weller p. 178 
1, la, lb, 2, 2a, 2b, 3, 3a, 3b, 4, 4a, 4b, 5, 5a, 5b. Pedicle, brachial, 
and anterior views of five specimens ilustrating the youthful 
stages of development. Brentwood limestone, Station 134. 
6, 6a, 6b. Pedicle, brachial, and anterior views of an individual of 
average size. Hale formation. Station 136. 
7, 7a, 7b, 8, 8a, 8b. Pedicle, brachial, and anterior views of two in- 
dividuals above the average size. Brentwood limestone. Station 
150 
9, 9a, 9b, 10, 10a, 10b, 11, 11a, 11b. Pedicle, brachial, and anterior 
views of three specimens illustrating the occasional develop- 
ment of a fold and sinus. Hale formation. Station 137. 
Figs. 12-12b. DIELASMA ARKANSANUM Weller p. 180 
12, 12a, 12b. Pedicle, brachial, and anterior views of a typical speci- 
men. Brentwood limest'^ne. Station 134. 
Figs. 13-13b. GIRTYELLA ? EMARGINATA n. sp p. 180 
13, 13a, 13b. Lateral, pedicle, and brachial views of the most com- 
plete of the cotypes, an internal cast, x2. Kessler limestone. 
Station 209. 
Figs. 14-15b. DIELASMA BILOBATUM b. sp p. 179 
14, 14a, 14b, 15, 15a, 15b. Pedicle, brachial, and anterior views of 
the two cotypes. Brentwood limestone. Station 134 
Figs. 16-16b. BRACHYTHYRIS LATICOSTA n. sp p. 187 
16, 16a, 16b. Pedicle, brachial, and lateral views of the holotype; the 
brachial valve is slightly crushed against the pedicle valve. 
Morrow formation, Station 297. 
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