NATURAL SCIENCES OF PHILADELPHIA. 339 



piece, inserted obliquel}' under one side of the first radial of the right posterior 

 ray, and connecting with the only other anal piece above by a short oblique 

 truncation of its right lower margin. This subaual piece varies in its propor- 

 tional size, even in difierent individuals of the same species, and is sometimes 

 very small, or even occasionally wanting, while it is very rarely, if ever, 

 large enough to separate the first radial and the true anal piece above 

 entirely from each other. A more constant difference, however, is the uniform 

 presence of but two of the free primary radial pieces to each ray (instead of an 

 irregular number), excepting perhaps sometimes in the anterior ray, where 

 there may be one or two more. These free radials are also proportionally wider 

 and shorter than in the typical forms of Cyathocrinus, particularly the second 

 radial, which is often so short and wide as to present a nearly transversely 

 linear appearance, as seen on the outer side. 



As in Cyathocrinus, the species of this group have their arms and all their 

 divisions composed each of a single series of pieces, apparently without pin- 

 nuhe ; but here these pieces are alwaj's very much stouter, distincth* rounded, 

 and only provided with comparativelj' very small, or almost linear ambulacral 

 furrows. Again, they present marked differences in their method of division. 

 That is, instead of regularly dichotomizing, so as to form equal divisions more 

 or less frequently subdividing in the same way, the subdivisions regularly di- 

 minishing in thickness, they are often simple from their origin on the last ra- 

 dials, and merely give off along their inner lateral margins, at regular intervals, 

 alternately on opposite sides, stout, rounded, simple armlets. In some instances 

 one arm of each lateral ray, and sometimes one of each posterior ray, dichoto- 

 mizes once or oftener, but even in these cases the other arms remain simple, 

 and, like the principal branches of those that bifurcate, merely throw off alter- 

 nately, at regular intervals along their inner lateral margins, stout armlets. If 

 these armlets in this group performed the same offices as pinnulaj in other 

 Crinoids, as we have everj' reason to believe the ultimate subdivisions of the 

 arms in Cyathocrinua proper did, the sacks for the reception of the ova must 

 have protruded considerably beyond the edges of the merely linear ambulacral 

 furrows. 



In the column of Barycrimis we also observe some more or less defined differ- 

 ences from that of Cyathocrinus. For instance, in the former group it is pro- 

 portionality stouter, with a much larger canal, which is also rarely, if ever, 

 perfectly round, but apparently always obtusely subpentagonal. But the most 

 remarkable difference consists in its being often divisible longitudinally into 

 five sections in Barycrinus. This character is not always well marked, being 

 apparently sometimes obliterated by the sutures becoming anchylosed. In 

 some cases, however, it is so strongly defined that we find the column with 

 these sutures more or less separated along its entire length, and in some spe- 

 cies there were apparently pores passing through these sutures to tlie cavity 

 within. We are aware that several other types of Crinoids had the column in 

 this way divisible into five parts longitudinally, but we have not seen any in- 

 dications of it in the typical forms of the genus Cyathocrinus. 



In regard to the vault of this group nothing is known, not a single individual 

 of the numerous specimens belonging to various species hitherto found, show- 

 ing, so far as we are aware, any traces of it. From this very fact, however, it 

 seems probable that its vault differed from that of Cyathocrinus proper in being 

 merely a soft ventral disc, without any covering of calcareous plates. If it 

 had possessed the power of secreting vault pieces, it seems probable, from the 

 thick ponderous nature of all its other parts, that these would have been suffi- 

 ciently firm to have been found in place, in some of the numerous specimens 

 now known. In addition to this, the upper inner edges of the first radial pieces, 

 on each side of the free radials, are beveled off to an obtuse edge, and show no 

 facets for the attachment of vault pieces. 



Whatever may be thought in regard to this group being entitled to rank as 

 a distinct genus, or as a subgenus, from Cyathocrinus, we can only say that the 



1868.] 



