cragin.] AGE OF MALONE FAUNA. 19 
Locality No. 10. — Foothill west of Malone Mountain, about 2 utiles north of its 
southern end; possibly same horizon as that of the preceding locality. 
feryphsea mexicana. Astarte malonensis?. 
Exogyra potosina (narrower phase). Lucina potosina, var. metrica. 
Peeten insutus. Pleuromya inconstans. 
Pinna quadrifrons. Perisphinctes aguilerai. 
Locality No. 11. — Near southern end of Malone Mountain, west face, near top; 
stratigraphic relation obscure. 
Trigonia niunita. Nerinea goodellii. » 
Locality No. 12. — Conglomerate on west face and near top of Malone Mountain. 
Trigonia goodellii? (east, larger than other specimens of this sp.) 
Locality No. 13. — East slope of Malone Mountain near the southern end; 200 
or 300? feet above the gypsum. 
pryphsea mexicana. Oppelia fallax?. 
Trigonia prsestriata. Perisphinctes clarki., 
AGE OF MALONE FAUNA. 
The affinities of its fauna clearly refer the Malone formation to 
the Jurassic. The only evidence that at first thought might seem 
discordant is the occurrence of the genus Ptychomya, which, with one 
or two doubtful exceptions, has not been recorded hitherto from rocks 
older than the Cretaceous. But when it is remembered that, of the 
Cretaceous Ptychomyas, only one species occurs later than the Lower 
Cretaceous (Neocomian and Gault) and that this one, the Pt. zitteli 
; of the western Alps, is from the Turonian, no species occurring in the 
higher (Senonian and Danian) stages of the Cretaceous, the occur- 
rence of one or two species of Ptychomya in the upper part of the 
Jurassic is only that which it would be reasonable to anticipate. 
This genus occurs at Chilian, Chile, in rocks of debatable age, and it 
is thought by Doctor Steinmann to have been derived there possibly 
from the same bed that yielded his Trigonia transitoria, from which 
T. vyschetzkii is scarcely distinguishable. The T. transitoria occurs 
also at Caracoles, Bolivia, where, on the basis of the kind of rock 
attached to the specimen, Doctor Steinmann supposes it to hail from 
the Lower Cretaceous; but nearly all of the Mesozoic fossils that he 
lists from Caracoles he considers Jurassic. 
The sections Undulatce and Costatm, to which several of the Malone 
Trigonias belong, are exclusively Jurassic, and, if we except Tri- 
"By Pictet and Campiche (Pal. Suisse; Terr. Cret. de St. Croix, p. 360. 1866) and 
Stoliczka (Pal. Indica; Cret. Fauna S. Ind., vol. 3, p. 311. 1871), the section Undn 
latw is said to include some Cretaceous species, but by later authorities it is cited as 
exclusively Jurassic. Thus it occurs, according to Zittel's Handhuch (1881-1885) " Nur 
in Jura;" and according to Steinmann and Doderlein's Elemente (1890), " Oberer Lias — 
Oberer Malm." 
