70 The Saint Peter Sandstone. 



been destroyed since the sandstone was deposited. One 

 might dig up many fossils without seeing them unless care 

 betaken to prevent the casts from being crumbled. The 

 most favorable conditions are in the somewhat infiltrated 

 strata where firmness is secured. 



In many cases the shells of bivalves are found in such a 

 manner as to prove that the ligament still bound them to- 

 gether at the time they were deposited in the sand. Of 

 course such shells could not have been transported far nor 

 much beaten about otherwise they would be found separ- 

 ated. Many of the shells were undoubtedly very thin and 

 fragile. 



LAMELLIBRANCHIATA. 



Genus Cypricardites. 



Cypricardites {Vanuxemia) fragosusn. sp. 

 Plate II, figures 1, 2 and 3. 



Cast acutely ovate in outline. Beaks extending beyond the anterior 

 end of the hinge, gently curved, gradually expanding, and swelling out 

 dorsally above the cardinal line. Casts concave under the beaks. Cardinal 

 line curved and extended into an alate projection at the anterior end in 

 front of the beaks but rounding evenly into the semicircular posterior mar- 

 gin. Antero-ventral margin slightly curved. The anterior alation contains 

 the cardinal teeth four or five in number and has a very deep muscle scar 

 just below it. Posterior muscle scar and posterior teeth not known. Along 

 the anterior margin the shell is concave, between the beaks and the poster- 

 ior ventral portion it is convex, end strongly so along the cardinal region. 

 Transverse length of largest specimen 30 mm., breadth greatest at the pos- 

 terior extremity of the hinge (18 mm.), convexity of single valve 12 mm. 

 Shells probably very thick. 



Found at Highland Park and South Saint Paul. 



Cypricardites descriptus n. sp. 

 Plate II, figure 7. 

 Small, stronglj-- convex, subquadrate, length 11 mm, breadth 9 mm. 

 Beaks anterior, acute curved in. The point of greatest convexity is near 

 the umbones, and the slope to the ventral margin is gradual. Cardinal 

 line gently curved. Pallial lime simple aad marked. The posterior muscle 

 sears large, situated just below the extremities of the hinge. Surface 

 smooth. 



Highland Park. 



Cypricardites ftnitimus n. sp. 

 Plate II, figure 6. 

 Shell of medium size, oblique, moderately convex, broadest posteriorly. 

 Beaks broad, a little projecting, and slightly coiled. The point of greatest 



