Description of Twelve New Fossil Species. 115 



The illustrated flattened specimen shows the basal plates united, 

 forming a hexagon. The six first radials are hexagonal, wider than 

 high, lower and upper margins parallel, and the lower a little longer 

 than the upper. Four of the second radials are hexagonal and the 

 other two appear to be pentagonal, one of them is certainly pentagonal. 

 Five of them are wider than high, while one pentagonal plate is higher 

 than wide. Five of the third radials are represented, each of which is 

 pentagonal and supports, upon its upper sloping sides, two secondary 

 radials. Beyond this, we can only trace part of the plates, which are 

 supported by two of the radial series, and if the pentagonal second 

 radial is upon the azygos side, then we have the posterior radial series, 

 and the right posterior radial series. The first secondary radials in 

 these series are heptagonal, except the one, upon the right of the right 

 posterior series, which seems to be hexagonal. The second secondaiy 

 radials are hexagonal, and as far as can be observed appear, each, to 

 support three radial series. This would give to a specimen, if there 

 was no irregularity, thirty arms. But we find the arms, thrown, in 

 clusters of three, only part of the way around the body, the arrange- 

 ment being disturbed, upon the azygos side; the actual number of arms 

 is only twenty-seven. 



Four of the first interradials are hexagonal, the other two are hep- 

 tagonal, andjoin the pentagonal second radials. The first interradials 

 are each succeeded by two second interradials, and these by three 

 third interradials. Above the third series of interradials, smaller 

 plates fill the space, between the secondary radials. 



The first and second radials and the first interradials are within the 

 columnar depression, and are either flat or slightly convex. The 

 third radials, the first secondary radials and the second and third in- 

 terradials are strongly tuberculated, or rise into little cones and form 

 a rim midway between the column and the arms, from which the plates 

 ascend, upon one side to the arms, and upon the other, up into the 

 columnar depression. From this rim to the arms, the plates are either 

 highly convex or conical. The illustration of the basal view of a speci- 

 men, in which the plates are firmly anchylosed, is intended to show this 

 rim and the conical plates. The part of the column preserved in this 

 specimen is no doubt pushed to one side of its natural position. 



The arms are unknown, except at the point of attachment to the 

 body. There are twenty- seven, as above mentioned. 



The dome is quite convex, and covered by a great number of small 

 convex plates, of unequal size and irregular form. A plate upon the 

 apex of the dome is a little larger than the others, and is surrounded 

 by about twelve small plates, but no order of arrangement of the plates 



