32 



Vault highly convex, covered with rather large, polygonal, plain, 

 smooth plates, and bearing a small, subcentral proboscis. The 

 ambulacral openings are directed a little above a horizontal line, 

 and may be seen in a summit view. No ovarian pores discovered. 



This species bears little or no resemblance, in general form or 

 surface features, to B. hodgsoni, the only thirteen-armed species 

 heretofore described, and cannot be mistaken for it. Its nearest 

 affinity seems to be with B. dodecadactyltis, Meek & Worthen, 

 from which it is distinguished by having thirteen instead of 

 twelve ambulacral openings to the vault, and one more secondary 

 radial in one of the rays. This alone is sufficient to distinguish 

 it as a species. It has also an extra, elongated plate, constituting 

 the third range in the azygous area, that does not exist in B. 

 dodecadaciylus. There are minor features in which they differ, 

 but these constitute the essential differences. In de'-cribing B. 

 dodecadaciylus, in Geo. Sur., 111., Vol. II, p. 205, the third radi- 

 als are described as "hexagonal." This is an accidental mistake, 

 or typographical error, for they are all pentagonal in that species 

 and in this one. 



Found in the Burlington Group, at Burlington, Iowa, and now 

 in the collection of S. A. Miller. It also occurs at Sagetown, 

 Illinois, and is in the collection of F. A. Sampson, from that 

 place. 



BATOCBINUS GLABER, n. sp. 



Plaie I, Fig. 26, azygous view of a medium specimen; Fig. 27, 



opposite view of same; Fig. 28, opposite view of a 



large specimen. 



Species varying in size from small to very large. Fig. 28 rep- 

 resents one of the largest specimens. Fig. 26 represents a medi- 

 um-sized specimen. Others, among a collection of thirty speci- 

 mens belonging to this species are not more than half as large 

 as the medium-sized specimens. The vault is usually as long or 

 longer than the calyx, but having somewhat less capacity. The 

 calyx is somewhat saucer-siiaped, constricted broadly at the first 

 radials and rapidly rounding up to the ambulacral openings, 

 which are directed upward at an angle of about forty-five degrees 

 and are not visible in a basal view. Surface of the plates plain 

 and smooth, occasionally the larger plates may show a slight 

 convexity. 



