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POTERIOCRINUS ARRECTARIUS, n. Sp. 



Plate IV, Fig. 6, azygons side view, showing part of the proboscis. 



Species medium size and not constricted above the calyx. 

 Calyx obconoidal. Sutures distinct. Surface smooth or finely 

 granular. 



Basals partly broken away from our specimen, but enough is 

 preserved to show that they form an obconoidal cup. Sub- 

 radials large and longer than wide. First radials nearly as 

 long as wide, pentagonal, truncated the entire width above, and 

 separated from the second radials or first brachials by a very 

 slightly gaping suture. Second radials or first brachials sub- 

 quadrate, as long as wide and slightly constricted in the mid- 

 dle. Third radials or second brachials a little shorter than the 

 first, very slightly constricted in the middle, axillary, and sup- 

 port upon the upper sloping sides the free arms. The arms 

 do not bifurcate and there are, therefore, ten arms in this spe- 

 cies. The arms are long, slender, and composed of a single 

 series of cuneiform plates that bear small pinnules. The pin- 

 nules are from the inside of the arms so as to allow the arms 

 to come together. 



The azygous plates alternate, as is usual in this genus. The 

 first plate is the largest and rests upon the upper sloping sides 

 of two subradials, separates the first radial on the right from 

 the second azygous plate and is truncated on top by the third 

 azygous plate. The second plate is somewhat smaller than the 

 first, hexagonal, and only slightly truncates a subradial. The 

 azygous area above these plates is wide and terminates in a 

 wide and long proboscis that, in our specimen, extends beyond 

 the parts of the arms w T hich are preserved and appears to have 

 extended beyond the tips of the arms. The proboscis is fluted 

 and punctured with longitudinal rows of pores between the 

 longitudinal series of plates of which it is composed. 



This species is distinguished by its general form, structure 

 of the arms and character of the proboscis. 



Found by the late Wm. Mc Adams in the St. Louis Group, at 

 Alton, Illinois, and now in the collection of Wm. F. E. Gurley. 



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