374 bulletin: museum of comparative zoology. 



achieving any prominence; occasionally the only evidence of the outer 

 plication is a sinuosity in the lateral margin. The brachial valve is 

 characterized by a short and not prominent fold divided by a median 

 furrow. On each side there may be one or two short plications. 

 The fold, sinus, and plications on both valves are short, not extending 

 one half the length of the specimen. 



05 a^ 



®(g)^<s>ooo 



Fig. 3. Nine serial sections of the rostral portion of a specimen of Camarophoria obesa 

 Clark. Natural size. 



Internally, the pedicle-valve shows a pair of dental lamellae near the 

 beak, supported by a median septum. The lamellae are continued 

 anteriorly into a spondylium, well raised from the floor of the valve. 

 The brachial valve has a slightly longer median septum supporting 

 both hinge-plate and cruralium. The hinge-plate is short, and the 

 cruralium extends a short distance beyond the septum. 



The surface of the valves is unornamented save for lines of growth 

 placed at irregular intervals. 



This species resembles somewhat C. explanata (McChesney) which 

 occurs in the Chester group of the Mississippi Basin. That species, 

 however, is wider than long, has more prominent plications, and a 

 broader and, indeed, very wide fold and sinus. C. obesa has a much 

 more prominent beak. 



Horizon and locality. — Professor J. B. WoodWorth and the writer 

 have collected this species from the Madison limestone at Old Baldy, 

 Montana. 



Axiodeaneia, gen. nov. 



Description. — Shells subovate to triangularly subovate in outline, 

 the valves subequally convex, the mesial fold and sinus slightly devel- 

 oped or obsolete. Both valves marked by broad, rounded or sub- 

 angular plications; when the surface is well preserved it is marked 

 by fine radiating striae. In the pedicle-valve the hinge-teeth are 

 small and are supported by slender, vertical, dental lamellae. In 

 the brachial valve a well-defined median septum is present in the 

 rostral portion of the valve, and is divided anteriorly to form a V- 



