KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:<> 2. 123 



and »recumbent pinnulae». As to the diagnostic value of a eoiled anal tube, I should not 

 be inclined to regard it as of more moment here than in the case of Botryocrinus cucur- 

 hitaceus. The pendent arms, or rather arm, fur only one is p reserved in the specimen, 

 are not miich to go upon. The proximal part of the arms was undoubtedly directed 

 downwards in some specimens of Cyathocrinus visbycensis; while there is nothing to show 

 that the distal part of the arms was not directed upwards, as usnal, in the type- specimen of 

 Streptocrinus crotalurus. Lastly »reeumbent pinnulae» simply do not exist; in this as in many 

 other points, Wachsmuth and Springers description is erroneous throngh no fanlt of theirs. 

 The genus, then, if it is to stånd, must be based on a surer fonndation. There 

 are reallv many featnres that separate it from Cyathocrinus, as that genus is now re- 

 stricted; these are the great width of the radial facet, the folding of the lateral plates of 

 the ventral sac, the radial sutures of the stem, and the presence of false pinnules. In 

 the first three of these points this form approaches sueh genera as Dendrocrinus, Mastigo- 

 crinus, Euspirocrinus and Botryocrinus, and it is clear that it should find a plaee some- 

 where in the Dendocrinidae or Decadocrinidse rather than with the Cyathocrinidae '). In the 

 structure of the dorsal eup this form elosely resembles Mastigocrinus, and differs from 

 all other genera of those families: it differs from Mastigocrinus, however, in the structure 

 of the ventral sac and in the character of the brachials, notably in the presence of false 

 pinnules. The ventral sac most elosely resembles that of Botryocrinus; while the perisomic 

 plates between the primibrachs on the ventral surface of the arms are parallcled in Euspiro- 

 crinus. The tegmen unfortunately cannot be seen, and the unique specimen is already so 

 fraetured that I have not dared to clean away more of the matrix. The arms too are in 

 so fragmentary a condition that the exaet systcmatic position of the genus must remain 

 doubtful for the present. Enough, however, can be gathered from the sjteeimen to enable 

 us to draw up the following — 



Revised generic disignosis. 



Dorsal Cup cyathiform. IBB 5, equal. BB ö: 4 hexagonal, post. B heptagonal. 

 RR 5, with wide articular facet. Arms apparently dichotomous; with some Br bearing 

 grooved processes (false pinnules). No R': x hexagonal, in line with RR. Ventral sac 

 composed of hexagonal plates, some of which are transversely folded. Stem round, with 

 small, pentagonal axial canal, and with radial sutures. 



As yet only one species of this genus is known. 



Streptocrinus crotalurus. 



(Plate II, tigs. 78—82, and Plate VI, tigs. 104 — 198.) 

 1878 Ojihiocrinus crotalurus Angelin, Iconographia, p. 2-1, Tab. IV, figs. 8, 8 a — c. 

 1886 Streptocrinus crotalurus Wachsmuth and Springer loc. vit. 

 Herpetocrinus scolopendrn Bather, This work p. 53. 



This species is based on a somewhat fragmentary specimen figured in Tab. IV, figs. 

 8, 8 a and the distal end of a ventral tube figured in figs. 8 6, 8 c. 



) Compare Brit. Foss. Crin. VII . Ami. Mag. Nat. Ilist., ser. (3, vol. IX, pp. 194—202; Mardi, 1892. 



