82 
SMITHSONIAN INSTITUTION 
I have given on plate 25, figures 27-27C, careful figures of the specimen used by Schultze 
as the type, to show the remarkable parallelism with Zophocrinus. The two forms differ 
widely in certain details. Tiaracrinus has a very small, concave base, apparently of 3 plates, 
and the surface of the cup is covered by 4 series of sharp, transverse folds passing from 
one radial to another, ending in deep pits forming vertical rows separated by a wide groove 
along the middle of each radial — in contrast to the perfectly smooth surface of Zophocrinus. 
The cup has 4 unequal radials, but instead of the posterior one being largest, it is sometimes 
the smallest. 
But the solid tegmen is constructed on precisely the same principle as that of Zopho- 
crinus, being composed of 5 orals meeting at the center and interlocking, with extensions or 
connections reaching to the periphery between which are 5 groups of extremely narrow 
plates, presumably brachials, springing from the radials and forming with the interposed 
oral extensions a conspicuous border around the margin. Instead of 3 to a group, the number 
of brachials here is ii or 12, and they do not coincide in position with the radials. Thus the 
4 radials, quinquepartite tegmen, and the peripheral border of narrow brachials, are the 
essential characters common to the two forms. The enlarged figure of this tegmen on plate 25 
shows some indefinite small plates at the outer angles of the orals which are not understood. 
As the structures are preserved in this unicpie specimen, some of the sutures are obscure, and 
these small plates are not to be depended on. 
The interpretation of the peripheral border of narrow plates in Zophocrinus has been 
somewhat of a puzzle. Those of Tiaracrinus represent the same element without doubt, the 
only difiference being their greater number, amounting to 55 or 60 instead of about 15. That 
they are brachials, in view of their form, and position relative to the radials, seems highly 
probable, and Bather’s suggestion that they may be compared with the arms of Catillocrinus 
accords with my own view. In both cases there would be the unusual feature of several arms 
originating upon a single radial, and in the Catillocrinidae we have a range in number of 
arms — from 12 to 57 — similar to that in the two genera under consideration, viz.: 15 to 55 
or 60.’- The distinct presence of fossae upon the distal face of the brachials in Zophocrinus 
indicates that they must have borne articulated arms. 
As to the systematic position of these genera Bather and Jaekel are in substantial agree- 
ment, placing Zophocrinus among the Monocyclic Inadunata, Avhile referring Tiaracrinus to 
the Cystidea (Lankester Zook, 1900, pp. 151, 20; Phylogenie und System, 1918, pp. 89, 99), 
the latter based upon the belief that the rows of pits up and down the middle of the radials 
represent pore-rhombs. There is no suggestion of pores on the smooth surface of Zophocrinus 
to call for a reference to the cystids, and the remarkable identity in essential calyx structure 
would seem to preclude placing the two genera in different divisions of echinoderms. It may 
be that the extreme specialization of the tegmen and arms common to the two is an indepen- 
dent development, but it seems more reasonable, and in better accord with the facts as now 
disclosed, to regard them both as aberrant crinoids, in some way related, and modified from 
the Silurian to the Devonian. 
Zophocrinus howardi S. A. Miller 
Plate 25, figs, ig-26 
Zophocrinus howardi S. A. Miller, 17th Ann. Rep. Indiana Dep. Geol., 1892, p. 642 (adv. sheets, 1891, 
P- 33). Ph 6, figs. 26-28; N. A. Geol. Pal., ist App., 1892, p. 683, fig. 1254. — Weller, Bull. Chicago 
Acad. Sci., 4, pt. i, 1900, p. 152, pi. 15, fig. 13. — Bather, Treatise on Zool., pt. 3, 1900, p. 151, fig. 63. — 
Graban and Shimer, N. A. Index Foss., 2, 1910, p. 474, fig. 1785. 
Type of the genus. The characters are fully stated in the general remarks. 
The species is rather abundant at the type locality, St. Paul, Indiana, but speci- 
1 Springer, On the family Catillocrinidae, Smithsonian Misc. Coll., vol. 76, 1923, p. 20. 
