D escription of Twelve New Fossil S2)ecies. 105 



The first range of plates extends a little less than half way around 

 the base of the rudimentary column on the anterior side. This range 

 contains about a half dozen small irregular plates. 



The second range is on the anterior side, and extends about two 

 thirds of the distance around the base of the rudimentary column. It 

 contains twelve irregularly pentagonal plates of somewhat uniform 

 size. 



The third range encircles the base of the bod^', and consists of 

 eighteen plates. These are ver}^ unequal in size, but all of them are 

 hexagonal except three upon the posterior side, which are pentagonal. 

 Onl}' five plates, in this range, abut upon the base of the rudimentary 

 column. 



The fourth range contains nineteen plates. These are unequal in 

 size and irregular in shape. They are pentagonal, hexagonal and 

 heptagonal. 



The fifth range consists of twenty-five plates, var^'ing in form from 

 pentagonal to octagonal. 



The sixth range consists of about the same number of plates. The 

 average size, however, being slightly increased. Onl}^ a part of the 

 seventh and eighth ranges are preserved. 



All the plates are very poriferous. 



This species was collected by Fred. Braun, Esq., in the lower part 

 of the Niagara Group, in Ripley count}^ Indiana, though the speci- 

 men illustrated is in my collection. 



HOLOCYSTITES BACULUS, U. Sp. 



Plate X., fig. 5, view of the left or ambulacral side, 

 fig. 5a, view of the summit. 



Body long, slender, subcylindrical and very gradually tapering in 

 the lower third to the column. The summit is prolonged, in the 

 direction of the ambulacral orifice, which is situated on the left side. 

 The prolongation is much more marked than in H. x)^'>'longus. This 

 orifice is subquadrangular and surrounded by five arms. The small 

 plates surrounding the orifice are not clearly determinable in our speci- 

 men. The next range which assists in the support of the arms, con- 

 sists of eight plates. Five of these are hexagonal; two of them ex- 

 tend to the mouth, on each side of the anal plate, and may therefore 

 be called heptagonal, as this adds a mouth-side to them; and the 

 eighth or anal pi ale, which is a long pentagonal plate, between the 

 two latter, and extending from the mouth to the smaller plates sur- 

 rounding the ambulacral orifice. It possesses a small anal apei'ture 



