414 PROCEEDINGS OP THE ACADEMY OP 



the striae gradually become sharp ridges, and the intervening belts deep fur- 

 rowsthese characters being especially strong at the anterior end; whole 

 surface marked by faint incremental lines. Greatest convexity of shell con- 

 siderably below the middle. 



Length 1-30 (100); height -55(42); convexity of left valve -24(18; 

 whole number of farrows on exterior 14. 



Localities. Hillsdale county at Jonesville, and S. E. S. W. \, Sec. 33, 

 Adams. 



Differs from C. complanata in its greater relative transverse dimension and 

 its vertical enrolment. It may yet prove to be a Grammysia. 



Edmosdia, de Koninck. 



Edmondia binumbonata, n. sp. Shell of moderate size, rotund-quadrate, 

 very tumid. Hinge line short, posterior to the beaks ; posterior margin form- 

 ing with it a very obtuse angle ; anterior slope straight, forming a rounded 

 right angle with the slightly curved ventral border which is nearly parallel 

 with the hinge line, and joins the posterior slope by a regular curve. Beaks 

 depressed and incurved ; greatest thickness through the middle of the shell ; 

 principal umbonal slope running to the posterior extremity of the ventral 

 border ; a subsidiary one running to the anterior extremity ; between these the 

 surface is subcylindrical ; anterior to them it descends abruptly to the ante- 

 rior margin, while behind them it sinks at first rather abruptly, and near the 

 posterior border presents a little flattening. Surface (of cast) marked by eight 

 or ten concentric furrows. Anterior lunule excavated. 



Distance measured along the principal umbonal slope -85 (100) ; length 

 from anterior to posterior extremity -85 (100) ; anterior slope -59 (69) ; con- 

 vexity of right valve -24 (28) ; angle between anterior cardinal slope and prin- 

 cipal umbonal line 70. 



Locality. Marshall. 



Closely related to E. scalaris, McCoy (Brit. Pal. Foss. 502, pi. 3 H, fig. 6), 

 from the carboniferous limestone of Lowick, but the anterior extremity is pro- 

 duced into a rounded angle instead of being truncated. 



Orthonota, (Conrad), McCoy. 



Orthonota rectidorsalis, n. sp. Shell of moderate size, tumid, elongate 

 transversely with subterminal beaks and gaping extremities. Hinge margin 

 straight, reaching nearly to the posterior extremity of the shell, somewhat 

 elevated ; ventral margin straight, and parallel with the dorsal ; posterior ex- 

 tremity truncately rounded, making with the dorsal margin an anterior angle 

 of 105 ; anterior end slightly gaping two-thirds the width of the shell, 

 rounded abruptly above, gradually below ; beak scarcely elevated above the 

 dorsal line, flattened, incurved, with a conspicuous lunule in front ; umbonal 

 swelling running to the lower posterior angle. Hinge apparently edentulous 

 and simple ; pallial and muscular impressions undiscernible ; a deep groove 

 runs from beneath the beak to the anterior extremity, which interrupts the 

 concentric lines shown on the interior of the shell. The cast shows five or 

 six very faint lines diverging from the beak along the superumbonal slope. 



Length 1-48(100); height -44(30); convexity of right valve -10 (7); 

 length of anterior end -25 (17). 



Locality. Moscow, Hillsdale county. 



This shell agrees tolerably well with Orthonota, as modified by McCoy. The 

 gaping extremities and general outline perhaps indicate affinities with Solen. 



Sangdinolites, McCoy. 

 Sangtinolites ujnoxiFORMis, n. sp. Shell small, compressed, transversely 

 ellipsoidal, with subterminal beaks. Hinge line straight, a little shorter than 

 the shell at both extremities ; hinge consisting only of a long, sharp, lami- 

 nar lateral tooth behind the beak. Anal margin obliquely subtruncate, as 



[Sept. 



