MKl.l.ir.KAM Ill \ I \ ""'.' 



\t. >-./ ,' .,. \\ Mil \\in.-ii it i- abo .1 ..... naiad it 1^ bowwor; rmdttj 



ugi-hed l.y it- Mirface markings, which an- lint visible on tin- ca-ts of that -per 

 an<l l.y it- le-> oblique anterior ami po-terior end- and more nearly parallel ventral 

 ami dorsal margin-. In M lall. which i- probably not a true .l/...//.</.,y,v/>-. the 



me-ial depression is much more di-tim t. t/ .,./ 1,-r ami more oblique | 



t.-iiorly. ami lia- more regular surface markings. 



formation ility. Miil<ll>- (liinl <if lh.' Tr.-n: !. Mini.. 



Miii.ini KTA. /(. jrp. 



I'l I 



Shell >iiiall. eloiiL-.iti- ovate, the. length twice the greatest or posterior hight. 

 V.tho thickest a little above the center, ratln-r uniformly convex, the umhonal 

 ri.lge ami me.sial ilepresion Leing l.oth nearly obsolete. B -mall, between one- 

 fourth ami one-tifth of the entire length from the anterior extremity. Dorsal margin 

 gently arcuate.' anterior eml narrowly Imt almost uniformly roumle<l. ventral edge 

 -tr.iight. posterior end slightly oblique, rather broadly rounded, most prominent a 

 little beneath the center, above which it curves forward gradually into the hinge 

 line. Surface with very line concentric line.-: these are equal and strongest near the 

 posterior can I inal bonier. Hinge very thin, edentulous. Mu-cular scars not ob-eivc.l. 



Length l:l.:l mm., posterior bight (i.(5 mm., anterior hight i> mm., thickness (left 

 valve only) about 2."i mm. 



I'onsiderably like, ami probably a near relative of M. nn/ufa. but ditler- in the 

 more uniform convexity of its surface, obsolete unibonal ridge and less oblique 

 anterior margin. The posterior end also i- comparatively narrower and the shell 

 -mailer. Ai-itlm-lf-i nitiilnln is a> S oci ;l t t >d but cannot be confounded, -ince it is a 

 -uiooth shell, with unequal valves, and much wider posteriorly. 



i/i/lf.-A- v ith PUthoeardia umbonati, Uatheria rnyota and otli 



marking il,. U|>IHT (art of 1 1,.. nu M . thinl <>( th.- Tr^nt..!! -hale* near Cannon Fall*, Mlnn.iw.ta. 



MODIOLOPSIS Co 



I'l. All \X\VI KIO8. 14. M. Ifa. 

 Mixtiolopnteoneai'i I I.I;K il, 1802. N " 37. 



Shell very small, elongate, the greatest hight a little les- than the length. 

 .ircu.it,-. the posterior end much the wide-t and broadly mumled. the anterior 

 exceedingly short, narrow and contracted beneath the beak-: the latter are small. 

 compressed, and project but little above the hinge. Might of posterior third about 

 two and one-half times as great as at the beaks. I>>r-um gently arcuate : 



thirds of ventral margin -tr>: >. a fact due in a great measure t<> 



