Loiver Silurian Fauna of Minnesota, 339 



scar smaller and less distinct. Palial line simple and very marked. From 

 posterior to the beak there runs a bold ridge about two-thirds the distance 

 to the anterior ventral margin of the cast. 



From the Orthisina beds at Saint Paul, Minnesota. 



The above described species is closely related to Cypricardites obtusa 

 Hall. Indeed, in the description of C. obtusa mention is made of a speci- 

 men, from northwestern Wisconsin, that has a ridge on the cast, and that 

 may be identical with the specimen described here. The shell figured by 

 Mr. Billings as Ctenodonta (Ambonychia) obtusa Hall, in general outline 

 at least agrees with the one that I have figured. 



But from the original description and figure, I am unable to decide 

 whether the above described or the following species is most nearly allied 

 to C. obtusa Hall. 



CYPRICARDITES VICINUS U. Sp. 



Plate VI, figure 22. 



Shell large and smooth as shown by casts of the interior and of the 

 exterior. Hinge long and straight. The anterior margin makes an angle 

 of 90" with the hinge : it is quite continuous with the ventral margin. The 

 ventral and posterior margins form rather more than a semi-ellipse. 

 Beaks anterior, scarcely incurved; umbones evenly rounded but high. 

 Shell thickest just back of the umbones. Cardinal teeth two or three, set 

 obliquely to the hinge line, and parallel to the three oblique posterior 

 teeth. The anterior muscle scar is deep, small and reniform ; the posterior 

 scar is larger but often not outlined. Palial line distinct. 



From the Blue limestone at Minneapolis. 



This species differs from the last described in being very much larger, 

 more elongate, and in having rounded incurved beaks and smoothly 

 rounded surface. It may be, however, an earlier form of the same species. 

 But no evidence to that effect is known to me, except their great resem- 

 blance. 



TELLINOMYA CANDENS n. Sp. 



Plate VI, figures 24. 



Shell very small, length 7 mm., breadth 4 to 5 mm,, moderately con- 

 vex. Surface smooth (?). Beaks anterior, small, oppressed, and coiled 

 inward and a little forward. Umbones prominent, hinge a little curved, 

 ventral margin arcuate and continuous with the anterior margin, the an- 

 terior margin curves more sharply up to the hingt line, posterior rounded. 

 Casts show two distinct muscle scars at the extremities of the hinge, and 

 a simple palial line. No cardinal teeth could be discovered. This species 

 is very common, but good specimens are rare. 



The specimens figured are from the Stictopora bed, at Minneapolis. 



TELLINOMYA ( Or NUCULA) LEPIDA n. Sp, 



Plate VI, figures 18, 19 and 20. 

 Compare Tellinomya (Ctenodoata) astartaeformia Salter. 



Shell small, length 25 mm., breadth 25 mm., surface smooth but three 

 or four varices of growth, beaks subcentral high, small, oppressed, closely 



