2l6 SMITHSONIAN INSTITUTION 



The most striking morphological feature of Sagenocrimis is one the taxonomic value of 

 which was overlooked until pointed out by me in 1902, and that is the presence of a radianal 

 interposed within the ring of basals, and usually touching the infrabasals. It thus occupies 

 the same position among the Flexibilia that Thenar ocrmus does among the Inadunata. The 

 plate is not so primitive as the radianal of Homalocrinus, which is directly under the right 

 posterior radial ; whereas here it is angular above, lying obliquely below the right posterior 

 radial, and abutting also upon the anal plate. Except in one species, the radianal is interposed 

 to a variable extent between the two basals, resting upon the infrabasal circlet. This fact 

 was observed by Angelin without comprehension of its significance ; he described the genus as 

 having " parabasalia sex," but his observation did not attract attention. The position of this 

 plate would seem on first thought to be the most primitive of all, but it is really not so ; for the 

 radianal has moved out of its original position as an infer-radial, and is no longer in contact 

 with the right anterior radial, but has become an element in the posterior interradius. Whether 

 it remains entirely between the two basals or not is purely a matter of degree in its develop- 

 ment ; its lower face varies in width of truncation, and if this narrows to a point the radianal 

 becomes rhombic instead of pentagonal, and no longer connects with the infrabasals (PI. XIX, 

 fig. 5). but its essential position relative to other structures remains substantially the same. It 

 is only a short step from this to an anal structure like that of Forbesiocrinus agassizi, where 

 the anal plate on the longer right shoulder of the posterior basal is clearly equivalent to the 

 radianal pushed upward with the enlargement of the posterior basal. Owing to the small size 

 of this basal in Sagenocrimis the radianal, even when lifted up from between the basals as in 

 the case above mentioned, is still below the level of the radial, touching its lower shoulder ; 

 whereas in Forbesiocrinus, by reason of the pronounced elongation of the basal this plate 

 lies above the level of the radial, resting upon its left shoulder. This marked contrast in the 

 proportions of the posterior basal in the two genera is a very important point in their 

 separation. 



Sagenocrimis differs from the antecedent genera of the family in having the inter- 

 brachial areas completely filled by numerous massive plates, joined to each other and to the 

 brachials of adjacent rays by suture ; these rise to the height of the upper secundibrachs, 

 thence passing in between the arm bases, and gradually into the plated integument of the 

 tegmen. They form with the brachials an apparently solid calyx wall resembling that of the 

 Camerata, and in this respect the type is the same as that of Forbesiocrinus. The arms in this 

 genus are relatively long and slender, and appear as if given off from the upper edge of the 

 massive calyx much like those of some Camerata. The stem differs from the prevalent type 

 in this group in having no enlargement or series of very thin colunmals at the proximal end ■ 

 it commences at the calyx with alternating ossicles of nearly equal diameter, and continues 

 cylindrical so far as known. 



The Austins in proposing the genus treated it as belonging to their family Periecho- 

 crinoidea. 1 Their generic description " was not very lucid, the dorsal side of the calyx being 

 unknown ; they relied chiefly upon the presence of a " plated integument, which extends 

 between their lower divisions (of the rays) in the same manner as the membranous web is 

 stretched between the toes of many aquatic birds," — a construction which they declare 

 " clearly proves them to belong to an undefined genus." This " plated integument " is only 

 the extension of the interbrachial plates in decreasing size between the rays and their divi- 

 sions, and probably does not refer to any tegminal structure observed by them. In addition 

 to Phillips's 5". expansus (which he had placed provisionally with the Actinocrinites) they 

 describe a new species, 5\ giganteus, of which the " body-plates (were) unknown," but in 

 which " a plated integument connects the lower portions of the rays." No further light was 

 thrown upon the essential characters of the genus until Angelin's time, although the type 



'Ann. and Mag. Nat. Hist., Ser. I, vol. 10, 1842, p. no. 

 -Ibid., vol. 11, 1843, p. 205. 



