PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 47 
Fig. 1, on Plate , represents one of the examples referred to, the 
principal portion of the figure showing a natural cast of the dorsal valve, 
with the umbonal portion of the ventral valve. In this figure the full 
length of the shell from back to front is not shown, but it is represented 
in the accompanying diagram, Fig. 2. 
WASHINGTON, D. C., December 3, 1879. 
NOTE ON ACROTHIELE. 
By C. A. WHITE. 
Among the fossils collected from Primordial strata at Antelope Spring, 
Southern Utah, by Mr. G. K. Gilbert and Mr. E. E. Howell, who were 
then coxnected with the explorations and surveys west of the 100th 
meridian, were a number of examples of a discinoid brachiopod. This 
form I described and figuied* under the name of Acrotreta? subsidua, 
referring it to that genus provisionally. None of the examples were in 
a condition to show all the generic characters clearly, but certain fea- 
tures in these shells indicated their possession of important differences 
from any genus then established and led me to suggest that they prob- 
ably represented a new goneric type. In the same year, 1876, Prof. G. 
Linnarsson, of Stockholm, Sweden, published} a new generic form from 
the Primordial rocks of Sweden, under the name of Acrothele, which 
plainly includes Acrotreta ? subsidua White. Professor Linnarsson des 
cribed two Swedish specics under this generic name (A. coriacea and A. 
granulata), and in 1879 he published a third species under the name of 
A, intermedia,t but A. subsidua is at present the only known American 
species. It is not unlikely, however, that some of the American species 
heretofore referred to Discina will be found to belong to Acrothele. 
WASHINGTON, D. C., February 1, 1889. 
DESCRIPTION OF A NEW CRETACEOUS PINNA FROM NEW 
MEXECO. 
By C. A. WHITE. 
Pinna stevensoni. 
Shell large, elongate-triangular in marginal outline; valves moder- 
ately convex; the convexity being slight and nearly uniform poste- 
riorly, but much greater toward the front, where it amounts to an obtuse 
median angularity upon each valve, and whee a transverse section of 
the shell has an approximately regular rhombic outline; upper border 
* Expl. and Sur. West of the 100th Merid:, Vol. IV, p. 34, pl. J, fic: 3, a,.b, ¢, and d. 
t Bihang till k. Svenska Vet. Akad Handlingar, Band 3, No. 12, p. 20, pl. IV, figs. 
44-52. 
+ Sveriges Geologiska Undersiékning; Ser. C. Afhand. och Upps. No. 35, p. 25, pl. 
lii, figs. 40-44, 
