m 



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

 scars of anibulacral 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 

 orifi:e, each is surrounded by eight plates. 



This species will be distinguished by its general form, great 

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

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

 spine bases, and sessile habit. 



Pound in the lower part of the Niagara Gi'oup near Madison, 

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



ORDER BLASTOIDEA. 

 Family CODASTERIDJE. 



CODASTER BLAIRI, n. Sp. 



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

 mit view, one triangular field in covered toiih part of the 

 matrix so that tlie asijgous opening cannot he seen. 



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

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

 Transvi'i'se section of the calyx i)entagonal with slightly con- 

 cave sides; surface marked with numerous fine lines paralhd to 

 the sutures between the plates, except the three longitudinal 

 sutures between the basals. Ti'uiicated at the base for a very 

 small, round column. 



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

 and ])entagonal, 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. Radials a little wider than liigh, equal, truncated above, 

 and mc^sial gibbosity gives the pentagonal outlin(> to the sum 

 mil. From a central, pentagonal, stelliform opening. fiv(> tri- 

 angular fields radiate to the angles of the i)entag(>nal summit. 

 The on(> wliich is smooth and bears the anal opening, in other 

 species, has part of the matrix attaclied 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 



