156 SMITHSONIAN INSTITUTION 



PLATE LXXV 



(All figures natural size except where otherwise stated) 



^ " PAGE 



Fig. I. Ptilocrinus pinnatus A. H. Clark 49, 52 



(For comparison of interbrachial structures and tegmens) 



Fig. la. Left anterior interradial view of calyx with part of stem ; showing the interbrachial peri- 

 some and the tegminal ambulacra in profile. X 2. 

 lb. Posterior view of same; showing anal opening at the apex; holes made by the boring 



parasite, Eulima ptilocrinicola Bartsch. X 2. 

 If. Tegmen of same ; the wide ambulacra, and relatively small orals separated from radials 

 and pushed to the center by extensive growth of perisome, the posterior one differen- 

 tiated by contact with plates surrounding the anal opening. X 4- 

 Recent : 1588 fathoms. Albatross, Cruise of 1890, North Pacific. 



Figs. 2-4. Cupulocrinus jewetti Billings 88, 89 



(Illustrating a possible Inadunate ancestral type for the Flexibilia. Figs. 2 to 6 

 reproduced from the author's paper on A Trenton Echinoderm Fauna, igio.) 



Fig. 20. Anterior view of calyx; showing the short and wide IBr and IIBr with strongly arcuate 

 sutures ; and small plates of interbrachial perisome between the rays. 

 2b. Posterior view of same, showing large RA under r. post. R ; and beginning" of the anal 

 series. 



3. Posterior view of a specimen with arms ; showing RA, and the vertical anal series 



separated from adjacent rays by perisome; arcuate sutures strongly marked. 



4. Posterior view of another specimen, showing the anal tube, with dorsal median series of 



large plates, curving distally upon the perisomic integument which borders it for its 

 full length. 

 Trenton; Ordovician. Kirkfield, Canada. 



Fig. 5. Cupulocrinus humilis Billings 88, 89 



Fig. S. a specimen showing tapering stem, and interbrachial perisome beginning with a fairly 

 definite large plate in the axil. X 2. 

 Horizon and locality same as last. 



Figs. 6a, b. Cupulocrinus minimus n. sp 88 



Fig. 6(7. Posterior view of specimen, with median anal series curving upon the tegmen and merging 

 into perisome only a short distance above the first ray bifurcation. X 2. 

 66. Distal view of same. X 2. A recurrent Trenton type from the Waynesville formation of 

 the Richmond group. 



Silurian. Waynesville, Ohio. 



Figs. 7, 8. Reteocrinus nealli (Hall) 90 



(For comparison as transition type of Camerata) 



Fig. 7. Posterior view of calyx, with undifferentiated tegmen of small plates ; ■ median anal 

 series bordered by perisome and leading to anal opening at margin of tegmen. X 2. 

 8. Oblique r. post, view of another specimen, with tegmen more directly seen ; anal opening 

 at the left. Note the entire absence of ambulacra. 



Silurian. Waynesville formation of the Richmond group. Morrow, Ohio. 



Fig. g. " Caleidocrinus " multiramus Barrande 442 



(Also on Plate LXXVI, fig. 24) 



Fig. q. a specimen from Zahoran, Bohemia, in which the substance of the plates is preserved; 

 showing the general form of crown and stem, low BB, and broad base. Belongs to 

 locrinus; see PI. LXXVI, fig. 24, for structure of anal side. 

 Ordovician, Etage D4. 



