THE CRINOIDEA 



199 



1897 ; Eucrinus, Ang.), Silurian, Europe and N. America (Fig. CXXIIL) ; 

 arms fork once or twice, are stout, biserial, and directed upwards. Cypho- 

 crinus, S. A. Miller (1892 ; syn. Hyptiocrinus, W. & Sp.), Silurian, Indiana ; 



IB 



FIG. CXX1I. 



Reteocrinvs Onealli, anterior view. 

 p, pinnules ; j3, fixed pinnules ; 

 other letters as usual. (After 

 Wachsmuth & Springer.) x . 



nn 



Fio. CXXIII. 



DimerocHnvs ilecculfcti/lus, from 

 Brit. Mus. EOT07 ; seen from pos- 

 terior interred ius. nn, nodals of 

 stem, x 2 diain. 



As 



arms fork at least once, are stout, biserial, and pendent, thus exposing 

 the tegmen which is spinous. FAMILY 3. LAMPTEROCRINIDAE. Dicyclica 

 Camerata with a dorsal cup in general structure like that of Dimero- 

 crinidae, but with asymmetry introduced by the 

 development of an anal tube and consequent 

 bulging of IR, and shifting of mouth anteriorly. 

 All from Silurian, N. America. Genera 

 Lampterocrinus, C. F. Roemer (1860, W. & Sp., 

 1897) ; IBB large, anchylosed ; anal tube cen- 

 tral ; arms supposed to be 5 rami bearing alter- 

 nate ramules, but are not known beyond IIIBrj 

 (Fig. CXXIV.). Siphmiocrimts, S. A. Miller 

 (1888, em. W. & Sp., 1897) ; IBB small ; rectum 

 forms an asymmetric protuberance below, then 

 curves subtegminally either to a central anal 

 tube, or right across to an anterior opening at 

 or even beneath the arm-bases. 



FAMILY 4. RHODOCRINIDAE. Dicyclica Cam- 

 erata with RR separated by a single distinct 

 plate in each IR, followed by well-defined iBr 

 regularly arranged (some individuals of Lyrio- c. F. Roemer.) x j. 

 crinus have RR not quite separated, and 



some species of Diabolocrinus have not the single distinct interradial) ; 

 the anal area is not always distinct, and but rarely has a vertical series of 

 plates. IBr, 2, in all except the rather doubtful Anthemocrinus. Arms free 



Fro. CXXIV. 



Isampterocrinus ten nesseensis, 



