LAMKLLIBBANi ill \ I \. 



.iiUln ] 



incurved in ca-K ..f the intci mr; in the sln-M projecting \.-ry little al.ove the hinge 

 line. . 1'iiil.onal ridge very indistinct. with tin- [mint of greatest c,,i,\exity a little 

 above ami in fmnt of the middle. in t lie ca^ts there is a more or less sharply defined 

 ami unusually wiile depressed or llatteneil strip running from the Leaks downward. 

 Hinge plate wide an<l strong, with two strong posterior lateral teeth in each valve, 

 and sometimes a third small one al.ove them in the left valve. Anterior teeth con- 



ig ..f one long tooth placed parallel with the margin of the shell in front of the 



beaks and five or six small unequal teeth running downward from the hori/ontal 



tooth. Ligament*] area well developed. Anterior muscular scar di-tiuct, elongate, 



'"allyd:- j immediately beneath the cardinal teeth. Posterior scar 



illy defined. Shell -iil-tanc thin, except in the anterior and dorsal region. 



The small vertically arranged anterior teeth, and the erect and strongly com- 

 pressed heaks of ca-ts of the interior are the two principal peculiarities of the 

 species. These and other equally obvious characters distinguish it from C. glubellu 

 I'lrich. '/// Hall, sp., often has the cardinal teeth broken up in a similar 



manner, but differs too obviously in other respects to render confusion between 

 them at all likely. 



nn.l l,;ilUj/.~1' te valves were collected by Mr. Cha*. Srhurh.-rl at . 



'"Mi.- "I Thiae are now In thi- tiui->i-iuii nf the Geological and Natural 



nesota. 



Mut. Reg. No. ." 



CLATA Ulrich. 



II I 108. 7 ud I. 



CypricariKtrifinijul'it.i i ,. 11 -UH-nth Ann. Rep^Gool. and NaU HUt Sur. Minn., p.tt6. 







MMu- the medium size, ventricose in the central and umbonal 



region, ol>li|ue. narrow anteriorly and broadly rounded posteriorly; the outline on 

 the whole, excepting a slight prominence at the postero-cardinal edge, almost regu- 

 larly ovate; hinge line rather short posterior to the beaks, slightly convex. Beaks 

 of good rongly incurved, projecting well above the hinge, situated a little 



more than one-fourth of the entire length behind the anterior extremity; umbonee 

 prominent, full, with an obtusa ridge or line of greatest altitude running from the 

 beak rds the postero-basal side: anterior and cardinal slopes both .-lightly 



ooacave. the latter descending more rapidly. Point of greatest convexity near the 

 middle of a line drawn parallel with and one third of the bight of the shell beneath 

 the hinge. Surface marked with v.-ry tine concentric line-. <. 'faded, and 



distant irregular lines or wrinkles of growth. Shell sub-tance thin. Internal c: 

 acter- unknown. 



-35 



