19 



ARCH^OCBINUS ASPEKATUS, U. sp. 



Plate II, Fig. 7, basal victo, azijgous side helotv; Fig. 8, suvimit 



view, azygous side below and matrix covering some of the 



plates on the right; Fig. 9, azygous side view. 



Species medium size. Calyx bowl-shaped, subpeutagonal in out- 

 line, more than twice as wide as high ; radial ridges interrupted 

 at the sutures ; plates subspiuous or very convex and more or less 

 sculptured ; surface grauular ; columuar cavity wide, deep, and 

 sculptured so as to indicate a pentagonal column. 



Basals small, deep withiu the calyx, but not covered by the 

 column, in fact, the column enters the cone formed by the basals 

 leaving the basals abutting the subradials outside the circumfer- 

 ence of the column. Subradials large, longer than wide, abruptly 

 bent iuto the columuar cavity and upward between the radials, leav- 

 ing a transverse ridge across the middle part of each, from each end 

 of which a radial ridge arises, that uuites with another iu the cen- 

 tral part of each first primary radial. The calyx will rest upon 

 these ridges as the sculpturing is deep. The azygous subradial is 

 octagonal the others are heptagonal, the shorter sides abut upon 

 the basals and adjacent subradials, the longer sides support the 

 radial series while each is rather broadly truncated at the super- 

 ior end. 



Three of the first primary raelials are pentagonal, the other two, 

 on the right of the azygous area, are hexagonal. They are all 

 wider than high, the shorter sides abut the interradials, the longer 

 sides the subradials and second radials. The superior side that 

 abuts the second radial is arcuate externally. The inferior angle of 

 each is sunk iu a deep pit, the central part of the plate is convex 

 from which a radial ridge extends to each adjacent subradial, while 

 the greatest prominence exists iu the upper part. 



Four of the second pi-imary radials are hexagonal and one pen- 

 tagonal, they are of unequal size aud vary from a little wider than 

 long to more than twice as wide as long. All of them are longi- 

 tudinally convex iu the central part and bear central nodes. The 

 third primary radials are smaller than the secoud, of unequal size, 

 pentagonal, axillary, aud support upon each upper sloping side 

 two small, short, secondary radials before reaching the free arms. 

 The secoud and third primary radials togetlier are not larger tiian 

 the first. The radial ridge iu each series continues across the 



