i8o 



SMITHSONIAN INSTITUTION 



PYCNOSACCUS Angelin 

 Plates XI-XIII 



Pycnosaccus Angelin, Icon. Crin. Sueciae, 1878, p. 13. — Von Zittel, Handbuch Palaeontologie, I, 1879, 

 p. 356; • Grundziige Palaeontologie, 1895, p. 138. — Wachsmuth and Springer, Revision Palaeoc- 

 rinoidea, pt. 1. 1879, p. 41 ; Proc. Acad. Nat. Sci. Philadelphia, 1890, p. 388. — Zittel-Eastman, 

 Textbook Paleontology, 1896, p. 164 (2d Ed., 1913, p. 203). — Weller, Jour. Geology, VI, 1898, 

 p. 700; Bull. IV, Chicago Acad. Sci., pt. I, 1900, p. 149. — Bather, Rep. British Assoc, for 1898 

 (1899), p. 923; Geol. Mag., (4)VIII, Aug., 1901, p. 378; Treatise on Zoology (Lankester), pt. 3, 

 1900, p. 187. — Springer, Amer. Geologist, XXX, 1902, p. 94; Jour. Geol., XIV, 1906, p. 484. 



Oncocrinus Bather, Ann. and Mag. Nat. Hist, (6)V, 1890, pp. 331, 332; Treatise on Zoology (Lankes- 

 ter), pt. 3, 1900, p. 187. 



Fig. 19. Pycnosaccus 



Lecanocrinidae with rays above radials separated by perisome only. Crown 

 short, calyx well differentiated. Infrabasals erect, taking part in calyx wall. 

 Radianal rhombic, obliquely to lower left of right posterior radial, resting on 

 basals. Large anal x followed by perisome. Interbrachial areas filled with 

 integument of small plates passing up into the tegmen. Primibrachs varying 

 from one to four, the first not filling distal face of radial. Rays arching over 

 interbrachial areas, but not in close contact. Arms dichotomous, divergent. 

 Column not enlarging proximally. 



Genotype. Cyathocrinites scrobiculatus Hisinger. 



Distribution. Silurian to Devonian; Sweden, England, the United States 



and Canada. 



Pycnosaccus, although a perfectly well-defined genus, has not been understood hereto- 

 fore owing to misinformation as to its real structure. Wachsmuth and Springer considered 

 it a doubtful subgenus under Lecanocrinns, there being nothing in Angelin's description or 

 figures to distinguish it from that genus except the presence of two primary radials (i. e., 

 one IBr) instead of three, and even on that point it was noted that Lecanocrinus sometimes 

 shows the same number. Von Zittel (Handbuch Pal., 1879) followed Angelin's diagnosis. 

 Bather (Lankester's Treatise on Zool., pt. 3, p. 187) placed it under the Ichthyocrinidae as 



