81 



is iu a higher or lower stage of developmeut thau its congener 

 B. roiundus, with twenty one arms. In short, we do not know 

 what, if any, specific characters, iu any of the genera, indicate 

 progress or decline, though we may uotice that Batocrinus, hav- 

 ing tumid plates, are more abundant and have a greater geolo- 

 gical range than those with smooth plates, and that twenty- armed 

 species arc more common than thirteen armed spicies. We must 

 not drift away from our mooring and forget that we have seen 

 only a small part f what the rocks have preserved, and that it 

 is possible, for others, in future, to see a thousand times as many 

 specimens as we have, with corresponding advantages for examin- 

 ing the structure, and drawing conclusions as to the evidences of 

 development. We attempt to speak only from the present state of 

 science and our own investigations. 



FAMILY POTERIOCKINIDtE. 



BARYCRIN0S SAMPSONI, n. Sp. 



Plide IV, Fig. 1, basal view; Fig. 2, azygous side. Fig. 3, op- 



posHe view. 



Species large, robusK Calyx about one and a half times as wide 

 as high. Plates very thick and highly convex. Angles of sutures 

 without pits. Column rather small, as shown by the cicatrix. 

 ISurface, apparently smooth, probably granular. 



Basals small and form a low, pentagonal cup or disc, with re- 

 entering angles. It is pierced by a small columnar canal, sur- 

 rounded by a cicatrix, for the attachment of the column, having a 

 diameter a little more than oue-third the greatest diameter of the 

 disc. The cicatrix bears five rounded, concave, radiately lined de- 

 pressions for the firmer adherence of the column. The plates are 

 quadrangular, without counting the side that abuts upon the canal, 

 and the adjoining sutures are beveled, so that the form of the 

 convexity of the plates is somewhat pyramidal. Subradials about 

 four times as large as the basals, as long as wide, highly tumid, 

 three hexagonal, two heptagonal, by reason of abutting the small, 

 intercalated, azygous plate, and the other octagonal, by reason of 

 abutting the two azygous plates. First radials about twice as large 

 as subradials, one-fourth wider than high, remarkably thick, and 

 broadly and deeply excavated for the attachment of the second 

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