Rekde.] Carboniferous Invertebrates. 119 



anterior extremity of the ear somewhat rounded ; posterior ear 

 separated from the margin by a larger and rounder sinus, and 

 from the shell by a nearly equal depression with that of the 

 anterior one ; the sides of the beak converge at an angle of 

 about 85 . The surface of the left valve is ornamented with ra- 

 diating strise, from three to six of which are marked at intervals 

 with vaulted, scale-like projections, give them a rough appear- 

 ance ; between each of these are four to eight smaller, slightly 

 ilexuous striae, increasing by implanation ; crossing all of these 

 are fine, closely set, concentric strise and occasionally larger 

 lines of growth ; anterior ear marked by radiating and fine con- 

 centric strise ; the radiating strise on the posterior ear are less 

 distinct. Measurements : Height, 21 mm. ; length, 29 mm. ; 

 convexity, 4 mm. ; length of the hinge line, 19 mm. 



Range and distribution : Upper Coal Measures ; Turner, 

 Lawrence, Lecompton, Topeka, Cowley county. 



This species can almost always be distinguished by its larger 

 ribs, with the vaulted scale-like elevations and smaller strise 

 between. Care must be taken, however, not to confound it 

 with Pst udomonotis, which it resembles to a considerable degree, 

 in an outward way, but it is much more regular and has the 

 ears better developed than in Pseudomonotis. 



Aviculopecten providencesis. Plate XIII, fig. 2. 



Pi cten providi ncesia Cox, Geol. Surv. Ky., in, p. 556, pi. viii, f. 1, (1857). 

 A uieulopecten providencesis Worthen, Geol. Surv. 111., viii, p. 116, pi. 



xxi, ff. 4, 4a, (1890). 

 Aviculopecten feiscu-uloius Keyes, Geol. Surv. Mo., v, p. 113, pi. xlii, f. 



7, (1894). 



Shell large, broadly subovate in outline, somewhat oblique ; 

 margins, except the ears, broadly and regularly rounded, the 

 beak extending very slightly beyond the hinge line, which is 

 shorter than the length of the shell ; height about equal the 

 length. Ears large, well defined, the posterior one much more 

 acute than the anterior, which is somewhat rounded, and sepa- 

 rated from the body of the shell by a somewhat shallow, distinct 

 sinus ; posterior ear separated from the swell of the umbo by a 

 sharp depression and from the margin by a distinct sinus. Sur- 



