white.] PALEONTOLOGY — CEETACEOUS FOSSILS. 293 



behind the anterior extremity ; posterior mnbonal slopes quite prominent 

 or subangular, and continued obliquely to the posterior basal angle, so as 

 to divide the surface of each valve into two nearly equal, elongated, in- 

 equilateral triangles, the lower of which forms the concave flanks ; an- 

 terior muscular scar small, but very deep ; posterior muscular scar larger, 

 shallow, suboval ; pallia! hue not distinctly seen, but apparently with a 

 small sinus. Surface with rather coarse, irregular marks of growth. 



" Length, 1.15 inches ; height, 0.55 inch ; convexity, 0.58 iuch. 



u Locality and position. — The specimen was given to Dr. Hayden at 

 the Salt Lake, and was found in that region, but he could not ascertain 

 the precise locality. It is almost certainly Cretaceous." 



There were three examples of this species found among the collec- 

 tions formerly in Mr. Meek's hands for investigation, of one of which 

 two views are given on plate x. Nothing further has been learned as 

 to their tine locality and position. Neither has anything further been 

 learned concerning the hinge or internal characters of the shell, but it is 

 probably correctly referred to Trapezium. 



Trapezium? micronema Meek. 



Plate x, fig. 5 a. 

 Trapezium micronema Meek, 1873, An. Eep. U. S. Geol. Surv. Terr, for 1872, p. 493. 



" Shell attaining a rather large size, elongate-trapeziform, the length 

 being a little more than twice the height, which is about one-third greater 

 than the convexity; anterior margin very short and round; posterior 

 margin obliquely truncated above and narrowly rounded below ; base 

 nearly straight, or faintly sinuous along the middle, rounding up rather 

 abruptly at each end ; dorsal margin long, straight, and parallel to the 

 base; beaks depressed nearly or quite to the horizon of the dorsal mar- 

 gin, and located one-sixth the entire length of the valves from the ante- 

 rior margin ; umbonal slopes prominently rounded from the beaks ob- 

 liquely backward and downward nearly to the posterior basal extremity, 

 while below this convexity a shallow concavity extends from each beak 

 obliquely backward to near the middle of the basal margin. Surface 

 with numerous very fine, regular, crowded, thread-like radiating lines. 



"Length, 2.28 inches; height, 1.21 inches ; convexity, 0.90 inch. 



"I know nothing of the hinge of this shell and merely place it in the 

 genus Trapezium from external characters. Its form and surface mark- 

 ings, however, are such as to leave little room for doubts in regard to its 

 relations to that genus or Goralliophaga. 



" Locality and position. — Cretaceous coal-bearing sandstones at Bear 

 Eiver City, on Sulphur Creek, Wyoming." 



No other than the type-specimen of this species has yet been discov- 

 ered, and consequently nothing further is known of its characters. 



Baroda wyomingensis Meek. 



Plate x, figs. 3 a and b. 



Tapes wyomingensis Meek, 1871, An. Eep. IT. S. Geol. Surv. Terr, for 1870, p. 310. 

 Baroda wyomingensis Meek, 1873, An. Eep. IT. S. Geol. Surv. Terr, for 1872, p. 493. 



The following is Mr. Meek's original description of this species, only a 

 single specimen of which has been discovered among the collections 

 examined by him, but that is evidently his type and only example. It 

 is figured on plate x. 



