88 
SMITHSONIAN INSTITUTION 
CALCEOCRINIDAE Meek and Worthen 
Calceocrinidae Meek and Worthen, Geol. Surv. Illinois, 5, 1873, p. 502. — Wachsmuth and Springer, Rev. 
Pal., 3, 1886, p. 273. — Ringueberg, Ann. New York Acad. Sci., 4, 1889, p. 388. — Bather, Crin. Gotl. 
1893, p. 54; Treatise on Zool., 3, 1900, p. 147 . — Crcmacrinidae Ulrich, 14th Ann, Rep. Geol. Surv. 
Minnesota, 1886, p. 105. 
Monocyclic Inadimata, with crown pendent or recumbent on the stem, in 
which the radials are connected with the base by muscular articulation instead 
of by suture, and in which bilateral symmetry, at first disturbed, has been 
progressively established by the location of the stem first to the right of the anal 
tube, and afterwards in the same plane ; anterior and left posterior radials large 
and simple; left anterior, right posterior and right anterior radials originally 
compound, the last two finally obliterated or non-arm-bearing; anal a- shifted 
over the right posterior radius, and supporting a massive anal tube; arms of two 
types, one (1. ant.) median, marking the plane of bilateral symmetry, and three 
lateral in early stage, afterwards, and finally, becoming definitely fixed at two, 
which are peculiarly modified by a doubly heterotomous mode of branching, 
wholly distinct from that of the median arm; basals first 4, later reduced by 
fusion to 3; calyx antero-posteriorly compressed, especially at the junction of 
radials and basals, where it is almost linear; transverse section about middle 
of radials triangular. 
Ordovician to Lower Carboniferous ; America and Europe. 
This singularly modified crinoid differs from all others by having the base united to the 
radials by a hinged muscular articulation, allowing motion of the crown above the base up 
and down in the plane of its bilateral symmetry. By this character, without precedent among 
the echinoderms, the family is set apart from the remainder of the class as a distinct zoological 
unit. Its morphology has been studied by Wachsmuth and Springer, Ringueberg, and Bather. 
The most extensive study is that of Bather, contained in his monograph on the Crinoidea of 
Gotland, 1893, which embodied an elaborate treatise on the family Calceocrinidae, with the 
advantage of the fine material from the Swedish and English Silurian, and is enriched with a 
wealth of beautiful figures drawn by the master hand of Georg Liljevall. No Silurian material 
at all comparable to that had been available to the American authors, nor has there been since 
until the collection herein described was assembled. In the treatment of the family, I have 
availed myself of Bather’s work, and of his later treatise in the Lankester Zoology, part 3, 
1900, page 147. 
The literature on the subject is difficult to follow, aside from the obscurity inherent in 
the anomalous structure, because the authors have employed different terminology for the 
parts which are peculiar to it. It is therefore necessary, before entering upon the discussion 
of a type of which the superficial appearance in its later stage is so widely different from that 
of other crinoids, to settle the orientation of the calyx. This depends chiefly upon the rela- 
tion of the radials, which are so greatly affected by the modifications that have occurred. 
Wachsmuth and Springer and Ringueberg treated the radius which is located between the 
two large radials, and thus occupies a conspicuous median position, and which had been called 
“ dorsal ” by Hall, as the anterior. Bather, on the other hand, regarded the median radius 
