86 



orifice and consists of eight plates, five of which bear the 

 scars of ambulacral spines, and one is inserted between the 

 mouth and the ambulacral orifice. The mouth is submarginal, 

 large and somewhat smaller than the very large ambulacral 

 orifice, each is surrounded by eight plates. 



This species will be distinguished by its general form, great 

 number of plates, none of which are intercalated, except the 

 triangular one that abuts upon the mouth, eight ranges, five 

 spine bases, and sessile habit. 



Found in the lower part of the Niagara Group near Madison, 

 Indiana, and now in the collection of Mr. J. F. Hammell. 



ORDER BLASTOIDEA. 

 Family CODASTERID^. 



CODASTER BLAIRI, n. Sp. 



Plate V, Fig. 20, basal view; Fog. 21, side view; Fig. 22, sum- 

 mit view, one triangular field is covered with part of the 

 matrix so that the azygous opening cannot be seen. 



Calyx obpyramidal, summit convex, so that the total length, 

 from column to summit, is equal to the greatest diameter. 

 Transverse section of the calyx pentagonal with slightly con- 

 cave sides; surface marked with numerous fine lines parallel to 

 the sutures between the plates, except the three longitudinal 

 sutures between the basals. Truncated at the base for a very 

 small, round column. 



There are three basals, the two larger ones are of equal size 

 and pentagonal, the smaller one is tetragonal and each has its 

 inner apex notched to form part of the round columnar canal. 

 The basals form a pentagonal cup about half the height of the 

 calyx. Radiais a little wider than high, equal, truncated above, 

 and mesial gibbosity gives the pentagonal outline to the sum- 

 mit. From a central, pentagonal, stelliform opening, five tri- 

 angular fields radiate to the angles of the pentagonal summit. 

 The one which is smooth and bears the anal opening, in other 

 species, has part of the matrix attached to it in our specimen, 

 so the anal orifice cannot be distinguished. Each of the other 

 four triangular fields is divided by a narrow angular radiating 



