48 



the second. What appears to be part of the top of the proboscis 

 may be seen at the summit of our specimen, but it is too im- 

 perfect; for description. 



This small species is peculiar and so different from all hereto- 

 fore described that the five arms alone will always identify it. 



Found by Prof. A. G. Wetherby in the Kaskaskia Group, in 

 Pulaski county, Kentucky, and now in the collection of Wm. F. 

 E. Gurley. 



ZEACRINUS DURABILIS, n. sp. 



Plate 4, Fig. 14, azygous side; Fig. 15, opposite view. 



This species is founded upon two specimens, in about an equal 

 state of preservation, but the one illustrated is one-half larger 

 than the other. The species is small and short, subovate in out- 

 line, being truncated at the base, sub fusiform in the middle, and 

 tapering toward the summit. 



Calyx very low, rounded and depressed below. Plates convex; 

 sutures distinct. Surface granular. Column small and round. 



Basals sunken so as to be hidden by the column. Subradials 

 longer than wide but hardly visible in a side view. First radials 

 about one and a half times as wide as high, pentagonal, truncated 

 the entire width above, and separated from the second radials by 

 a gaping suture. Second radials longer and larger than the first, 

 about one-half wider than high, rounded externally, pentagonal, 

 and support upon each superior sloping side the secondary radials 

 or free arms. In each ray adjoining the azygous area, there is a 

 single, long, secondary plate, on the distal side of the second 

 primary plate, that is axillary and supports an arm upon each 

 superior side, while an arm arises directly from the proximal side 

 of each second primary radial. This arrangement gives to each 

 of these rays three arms. The lateral rays are constructed in che 

 same way and each bears three arms. In the ray opposite the 

 azygous area there are only two arms which are supported on 

 the upper sloping sides of the second primary radial. The 

 species, therefore, has fourteen arms. The arms are short, small, 

 regularly taper, and are composed of small cuneiform plates. The 

 pinnules are short. 



The first azygous plate is narrow, elongated, pentagonal, rests 

 between two subradials and the first radial on the right, and abuts 

 upon the second and third interradials. The second azygous plate 



