CARBONIPEROTJS AGE. 41 



of the characters of his granosa. The apparent absence of grannies, however, on 

 the former may be due to the condition of the specimen, as this is a character easily 

 obliterated by wearing. Of the known foreign species, its nearest representative 

 is perhaps Sanguinolites variabilis, McCoy (Brit. Pal. Foss. pi. 3, F, fig. 6-7), from 

 ' which it differs in being much narrower posteriorly, and in having a proportionally 

 longer hinge line, particularly as compared with adult specimens of McCoy's species. 

 Its antero-ventral region is also more prominent than that of S. variabilis. 



Locality and position. — Leavenworth City, Kansas ; it occurs both in the hills 

 back of the town, 200 to 250 feet above the Missouri, and in beds of impure 

 limestone near the landing, little above the level of the river. Coal Measures. 

 (Type No. 1011.) 



8ed^wickia? concava. 



(Plate I, Fig. 8, a, 6.) 

 Lyonsia concava, Meek & Hatden, Trans. Albany Inst. IV, March 2d, 1858. 



Shell small, elongate-oval ; valves moderately convex in the umbonal and anterior regions. Extremities rounded ; 

 posterior end compressed, apparently a little gaping ; base nearly straight along the middle, and rounding up at 

 the extreuiities ; dorsal outline concave behind the beaks — declining in front. Beaks rather depressed, incurved, 

 and located about half-way between the middle and the anterior extremity. Surface of casts with a few more or 

 less distinct marks of growth. (Hinge, muscular and pallial impressions unknown.) 



Length, 0.65 inch ; height, from base to top of beaks, 0.30 inch ; convexity, 0.23 inch. 



In first publishing a description of this species, we placed it provisionally in the 

 genus Lyonsia, stating, at the same time, that bur specimens were merely casts, and 

 that we were consequently left in doubt in regard to its generic relations. Subse- 

 quent examinations of other specimens have satisfied us, however, that it can 

 scarcely be a Lyonsia — there being no impressions in well preserved internal casts, 

 of the projecting cartilage plates so characteristic of that genus. This being the 

 case, we now place it with doubt, in the genus Sedgioichia, to which it appears 

 to be more nearly related ; but in so doing, we should remark that until specimens 

 showing the hinge, and other internal characters can be examined, its true affinities 

 cannot be determined with any degree of confidence. 



Locality and position. — Nebraska, opposite the northern boundary of Missouri. 

 Coal Measures. (Type No. 1023.) 



!§ed^wickia ? altirofsitrata. 



(Plate I, Fig. 9.) 

 AUorisma9 altirostrata, Meek & Hatden, Proceed. Acad. Nat. Soi. Phila. Deo. 1858, 263. 



Shell longitudinally oblong-oval, very gibbous in the umbonal region ; beaks elevated above the cardinal margin, 

 incurved, and located almost directly over the anterior edge. Posterior side rather broadly and regularly rounded, 

 apparently gaping; anterior side subtruncate, a little gaping, and rounding into the base below; ventral border 

 nearly straight, or somewhat concave in outline near the middle, and rounding up at the extremities. Cardinal 

 margin straight, rather short. Surface of cast ornamented by concentric undulations, which are small, regular, 

 and well defined on the umbonal slopes, but become less distinct, and more irregular near the margins of the valves. 

 Just in front of the most prominent part of the oblique umbonal ridge of each valve there is a moderately distinct, 

 narrow, undefined sulcus, extending backwards and downwards to the middle of the base. 



Length, about 3.06 inches ; height, from the base to the dorsal margin, 1.57 inch ; do. to the highest part of 

 the beaks, 1.74 inch ; greatest convexity of the two valves, 1.62 inch. 



It is only provisionally we place this species in the genus Sedgioiclda, not having 

 seen any specimens showing the hinge ; while the form of the shell is different 



