6 



the second, pentagonal, axillary, and bear upon each superior 

 sloping side two secondary radials. The second secondary 

 radials are axillary, and, in three of the rays, bear upon each 

 superior sloping side a single tertiary radial, which gives to 

 each of these rays four arms. The distal side of each ray ad- 

 joining the azygous area is constructed in the same way, but 

 the proximal side of each bears an axillary, tertiary radial that 

 bears single quaternary plates, which arrangement gives to 

 each of these rays five arms. There are, therefore, twenty-two 

 arms in this species. 



There are three regular interradials in each area, one, fol- 

 lowed by two in the second range, which are cut off from the 

 plates of the vault by the union of the tertiary radials. The 

 azygous area is large and subovate. The first plate is in line 

 with the first primary radials and fully as large. It is followed 

 by three rather large plates, in the second range, three some- 

 what smaller, in the third range, and these by two smaller 

 ones, in the fourth range, that unite with a single, elongated 

 plate belonging to the vault. 



The vault is covered with large, convex, polygonal plates 

 and bears a subcentral proboscis. The proboscis commences 

 with rather large tumid plates, but its length is unknown. 



In general form this species bears most resemblance to B. 

 discoideus, but that species has only a single regular interra- 

 dial in each area, and only seven plates in the azygous area, 

 which is cut off from the vault by the union of the radial 

 plates. All other species from the Burlington Group having 

 twenty-two arms, heretofore described, are B. aspraiilis, B. for- 

 mosus, B. laetus, B. lepidus, B. sinnosus, B. iurbinatus, and B. 

 turbinatus var. elegans. While all these species may be distin- 

 guished by the general form, proportional size of the plates 

 and surface characters, they may also be distinguished by the 

 interradial and azygous areas. In B. aspraiilis, there is a sin- 

 gle large tumid plate in each regular area, and only five plates 

 in the azygous area, four of which are subequal in size, and 

 the other one is a small, quadrangular plate separating them 

 and resting on the first azygous plate. In B. formosus, there 

 are two plates in some of the regular areas and three in oth- 

 ers, and eleven plates in the azygous area. In B. laetus, there 

 are two plates in each regular area and six in the azygous 

 area. In B. lepidus, there are three plates in some of the 

 regular areas and four in others and twelve plates in the azy- 

 gous area. In B. sinnosus, there are from six to eight plates 



