33 



Basals form an hexagonal disc about one half wider than the 

 diameter of the column, aud bear a concave depression less than 

 hemispherical, for its attachment. First primary radials wider 

 than long and transversely concave, so as to give the appearance 

 of a constriction of the calyx, at this place. Second primary ra- 

 dials quadrangular, two or three times as wide as long. Third 

 primary radials a little larger than the second, three hexagonal 

 and two heptagonal, axillary, aud bear upon each of the two supe- 

 rior sides two secoudary radials, the last ones being axillary and 

 supporting, on each upper sloping side, two tertiary radials, which 

 arrangement gives to each of the rays four arms. There are, 

 therefore, twenty arms and twenty ambulacral openings to the 

 vault, in this species. The arm formula is 4-(-4+4+4+-4. 



The regular interradial areas are quite different from each 

 other. In one of the areas there are three plates, one, followed 

 by two in the second range, which are cut off from the vault by 

 the union of the first and second tertiary radials above them. In 

 each of the other three regular interradial areas, there are four 

 plates, one, followed by two in the second range, and by one in 

 the third range, but the plates are more elongated in some of these 

 areas than in others. In the largest specimens there is an addi- 

 tional plate iu the third range, so that there are five plates in 

 some of the areas and four in others. In the azygous area there 

 are twelve plates. The first one is in line with the first primary 

 radials and nearly as large. It is followed by three plates in the 

 second range, four in the third range, three in the fourth range 

 and one in the fifth range that separates the last tertiary radials. 

 There is some difference in the plates, in the azygous areas, in 

 different specimens, above the second range of plates, and the 

 number in the areas seems to vary from eleven to thirteen. This 

 is a feature that is noticeable in other species of Baiocrintcs, and 

 it may be laid down as a rule that the number of azygous plates 

 may vary, in the same species, but the number of ambulacral 

 openings will not change, within the limits of a species, except 

 as a result of injury or abnormal developments. 



Vault conoidal and bearing a subcentral proboscis. It is covered 

 with plain, smooth, polygonal plates. The ambulacral openings 

 are directed above an horizontal line and are visible in a summit 

 view. No ovarian pores have been discovered. 



