84 



Tho first azyg'ous plate is hexagonal, as wide as long, very 

 tumid or bulged out in the central part, rests between the 

 upper sloping sides of two basals, separates two first radials 

 and is followed by two plates that are not preserved in our 

 si)ecimen. The two superior faces are concave. The vault is 

 unknown. 



This species is extraordinary because there are only four 

 arms; because the first azygous plate rests between the upper 

 sloping sides of two basals, and because the plates are pitted. 

 The specimen is well jireserved and in its normal condition. 

 The hole .shown in the illustrations does not a})pear to pass 

 through the test and may not properly ijolong to the species 

 as a character of any importance. 



Pound in the Niagara Group, at St. Paul, Indiana, and now 

 in the collection of Wm. P. E. Gurley. 



ORDER CYSTOIDEA. 



Family HOLOCYSTID^E. 



HOr.OCYSTITES ASPEK, n. S]). 



Vlate V, Fig. 1, summit view: Fig. 2, anierior side view. 



Body miMlium size, subovate most tumid on tlic left anterior 

 side, plates large, convex, covered with largo pastules and 

 pierced witli numerous pores; sutui'es decjily impressed. The 

 specimen illustrated has the lower part broken away, so whether 

 or not it was sessile cannot be deterinined, and probably two 

 ranges of jilates are gone; five ranges of i>lates only are pre- 

 served. 



The tii-st range of plates preserved, which is, in fact, the 

 second or third range, consists of four large plates and four 

 smaller ones, the latter are on the anterior side and may be 

 seen at the bottom of figure 2. The second range has eleven 

 plates, of unequal size; the third range has eleven plates, the 

 foui'th range six, and the fifth range, tliat sun-ounds the ambu- 

 lacral orfice, at the center of the summit, has six plates. There 

 are no intercalated jilates between the ranges in our specimen. 



The mouth is sui'rounded by five ])lutes and is submarginal 

 between tlie range that sui-i'ounds the ambulacral orifice and 

 the next range below. Pour o! the plat's that scrround the 

 ambulacral orfice have spine bases. 



