23 



last being axillary and supporting on each upper side a tertiary 

 radial, and on the other proximal side one secondary radial, which is 

 axillary, and supports on each upper side a tertiary radial, which 

 gives to each of these two rays three arms. There are. therefore, 

 twelve arms in this species. The arm formula is 3+2 -j 2+2+3. 



In each of three regular interradial areas there 1 are three plates — 

 one in the first range and two in the second, both of which connect 

 with the plates of the vault; in the other area there are four plates, 

 two of which connect with the plates of the vault. In the azygous 

 area there are seven plates. The first is in line with the first primary 

 radials and fully as large as either of them. It is followed by three 

 plates in the second range, the middle one of which connects with 

 the plates of the vault. On the left of the upper part of this elon- 

 gated plate there is one plate that connects with the vault, and on 

 the right there are two plates, one of which connects with the vault. 

 There are, therefore, three azygous plates, in a wide area, that con- 

 nect with the vault. 



The vault is pyramidal, by reason of being depressed in the in- 

 terradial areas, and bears a large central proboscis. It is covered 

 with convex, polygonal plates. 



This species is so distinct from all other twelve-armed species, in 

 general appearance as well as in the general structure, that no com- 

 parison is necessary. 



Found by R. A. Blair, in the Burlington (Troup, near Sharon, in 

 Southwest Missouri, and now in the collection of S. A. Miller. 



BATOCR1NUS RUSTICELLUS. 11. Sp. 



Plate 7. Fig. is. basal view; Fig. 19. same, magnified two diam- 

 eters j Fig. 20, azygous side; Fig. 21, summit mew. 



We have three specimens of this species, one of which is twice as 

 large as the one illustrated. The species, may, therefore, be said to 

 be medium or slightly below medium in size, biturbinate or some- 

 what wheel-shaped, the larger specimen more wheel-shaped than the 

 one illustrated. Calyx very rapidly spreading at the arms: where it 

 is from two to two and a half times as wide as high. No radial 

 ridges, but the radial series are slightly lobed and project at the 

 margin so as to notch the circumference at the interradial spaces. 

 Plates plane and finely granular. Ambulacral openings not visible 

 in a basal view, but may be seen in a summit view. One ovarian 



