296 SMITHSONIAN INSTITUTION 



Angelin's time ; and the geographical distribution of the genus has been further extended 

 by the discovery of three well-marked species in America, extending its stratigraphic range 

 into the Lower Devonian. The four certain species may be arranged as follows : 



The Species of Clidochirus 



I. Surface ornamented with pustules and wrinkles. 

 Crown pyriform. 

 BB and IBB large. 

 RA about as large as RR. 



Br about 3 times wider than high C. pyrum. 



II. Surface smooth. 



Crown elongate, evenly curved. 

 Base narrow, BB and IBB large. 

 RA smaller than RR. 



Br less than 3 times wider than high C. americamts. 



Crown low, angular. 



Base broad ; BB and IBB small. 

 RA about equal to RR. 



Br strongly convex ; sutures indented C. keyserensis. 



Crown conical, evenly curved. 



Base narrow. BB and IBB large. 

 RA smaller than RR. 



Br 4 times wider than high C. schucherti. 



III. A variant with 3 IBr, perhaps of this genus, or a successor 



to it ; from the Lower Carboniferous (?) C. greenei. 



Clidochirus pyrum Angelin 

 Plate XXXVII, figs. 1-6 



Clidochirus pyrum Angelin, Icon. Crin. Sueciae, 1878, p. 12, pi. 22, fig. 23. — Springer, Jour. Geology, XIV, 



1906, p. 479, pi. 6, fig. 7. 

 Calpiocrinus pyrum Wachsmuth and Springer, Revision Palaeocrinoidea, pt. I, 1879, p. 39. 

 Ichthyocrinus piriformis Angelin (in part), Icon. Crin. Sueciae, 1878, pi. 17, fig. 6. 



Type of the genus. 



Species attaining a large size. Crown pyriform, with truncate base; ex- 

 panding gradually from base. Height to width at upper IIBr, 1 to 1 ; spread of 

 calyx from base to same level, 1 to 4 ; cross-section circular ; side outline straight 

 or slightly concave; no radial ridges; base relatively broad. Surface marked by 

 small pits on the lower brachials, becoming confluent above and forming numer- 

 ous parallel wrinkled grooves longitudinally disposed across the plates from 

 margin to margin. Medium crown, 24 mm. high by 18 mm. wide at top of 

 IIBn; base, 5 mm. 



IBB large, visible in pentagonal outline above the column. BB large, not 

 touching column ; posterior B larger than the others, and supporting two large 

 anal plates in vertical series, and sometimes a third smaller one; the upper one 

 angular above. RA about the shape and size of RR in other rays. Brachials 

 evenly curved; above IBr about three times wider than high, relatively narrower 



