290 The American Geologist. April, 1894 
with the overlying beds of the ( Colorado formation, and I have therefore 
treated them as the base of thai formation. 
So far as can be determined from a description withoul illustration, it 
is quite possible thai the fossil doubtfully referred to Placenticeras pla- 
centa is identical with P. syrtalis, var. cumminsi Cragin. However thai 
may be, ii seems to me i" be more closely related to P. placenta than to 
P. syrtalis. From the former it seems to differ in its smaller size and 
slightly less deeply divided suture, [f nol identical with this well 
known species from the Montana formation, it may at least he considered 
its direct ancestor. 
Prof. Cragin refers the "Modiola concentrice-costellata Roem.?"to 
his recenth described Modiola stonewallensis. This species, like a con- 
siderable number of others described as new in the "Contribution to 
the Invertebrate Paleontology of the Texas Cretaceous."' has never been 
figured, and ii is therefore gral ifying to have an example <>!' it identified 
by the author, who. ii is hoped, will take the first opportutity to illus- 
trate all his unfigured species. As to the validity of the name Modiola 
stoneicallensis, the figures of M. concentrice-costellata given by Roemer are 
very suggest ive of immature examples of this species, and their specific 
identity is made more probable b,\ the fact thai they come from the 
same horizon. 
The Texan species of Protocardia probably should not he referred to 
tin- European Cardium Mllanum Sowerby, although Roemer assigned 
them to that species. The fossils of this group, especially when not 
well preserved, show so few salient features that it is difficult to define 
i he limits of t he species. 
In his description of Astartt {? Steamsia) acuminata Prof. Cragin ad- 
mits that it is probably a synonym of Stearnsia robinsi White, and his 
figure, together with the fact that both c.ame from the same horizon and 
neighborhood, make their identity almost certain. "The radial marks 
seen on the beaks of Astartt acuminata, " as represented in the figure, 
look like an accidental feature. 
The young specimen of Trigonia emoryi Conrad is doubtless the young 
of T. elavigera Cragin, and therefore these two names are synonymous. 
The identification was made by comparison with the type of '/'. emoryi, 
which so closelj resembles the photographic figure of T.clavigera thai 
it might ha\e served as the original, excepting that the accidental de- 
fects in the two specimens do not quite coincide. 
Prof. Cragin isprobabh right in referring Arcopagia texana to <'ni>ri- 
iiKriti. though that reference can hardly he called unquestionable so 
long as the hinge of the species is entirely unknown. It would be inter- 
esting to know why any of the Fredericksburg Cyprimerias have been 
referred to C. era \ssi i Meek, which is a medium sized species from the 
Upper Cretaceous (Montana formation) of New Mexico. 
The queries as to whether certain specimens are types may be an- 
swered in saying that types, i. e. figured specimens, were not shown in 
the Geological Survey exhibit. T. W. Stanton. 
Washington, I). C, March s. 1894. 
