262 PROCEEDINGS OF THE NATIONAL MUSEUM, VOL. XXXIV. 
32 mm. Prof. D. W. Spangler found one specimen and Mr. G. S. 
Dodds found another, both in the sandstone member of the Fort 
Pierre Cretaceous.in Fossil Ridge, about 6 miles south of Fort Col- 
lins. 
The type is now in the U. S. National Museum (Cat. No. 30879) 
and the eotype in the University of Colorado cabinets. A juvenile 
example found by the writer at the same place shows that the apex 
is rather sharp. 
ANATINA DODDSI, new species. 
Pla XOUOL, ies, By 4h 
Shell of medium size, transversely ovate in outline, rather shortly 
rounded behind and more broadly so in front, very thin; posterior 
end gaping, gently contracted above and below to the meeting of 
the valves on the dorsal and ventral margins; dorsal margin deeply 
excavated immediately behind the beaks and shghtly concave imme- 
diately in front, thence sloping gently away and rounding some- 
what abruptly into the anterior margin; basal margin forming a 
broad curve, subemarginate as a result of the broad sulcus in each 
valve; beaks rather prominent, behind the middle, incurved and 
almost touching; valves moderately convex, greatest convexity be- 
hind the medial sulcus; surface marked by strong, rounded, equi- 
distant concentric undulations which nearly disappear on the pos- 
terior half, the interspaces of about the same width as the undula- 
tions; growth lines on and between the undulations visible without 
a lens, giving the undulations a rather irregular appearance; sides 
of valves divided by a broad, shallow sulcus extending from the 
beaks to the ventral margin, in and behind which are a number of 
sharp raised lines radiating from the beaks, some prominent, others 
indistinct; length of type, restored by comparison with other ex- 
amples, about 50 mm., height 35 mm., convexity of both valves 
united 17 mm. This shell closely resembles A. sulcatina (Shumard) 
Whiteaves in outline, but differs from the latter in the somewhat 
narrower posterior margin, the proportionately broader sulcus, and 
in the radiating raised lines which are observed on all of our examples 
from three different localities and three horizons. The latter fea- 
ture is not mentioned by Shumard or Whiteaves in their descriptions 
of sulcatina, but White has described and figured a specimen from 
Sucia Island which bears impressed radiating lines, thus being the 
exact reverse of ours in this respect. A very young specimen is 
much more pointed both before and behind. 
Mr. G. S. Dodds and the writer found the type-specimen, now in 
the U. S. National Museum (Cat. No. 30880) and another in the 
sandstone member of the Pierre Cretaceous at Fossil Ridge, 7 miles 
