BLASTOIDEA AND CYSTIDEA 
I4I 
The BLASTOIDEA and CYSTIDEA 
It has not been my intention to make a critical study of these two classes ; 
yet in view of their intimate association with the crinoids in the formations here 
discussed, it seems advisable to illustrate the more prominent forms which have 
appeared in the collections. These include two species of blastoids and seven of 
cystids. 
Troostocrinus reinwardti (Troost) 
Plate 33, figs. 1-8 
Pentremites reinwardti Troost, Trans. Geol. Soc. Pennsylvania, 1835, p. 224, pi. 10, figs. 9-12; sth Geol. 
Rep. Tennessee, 1840, p. 55. — Pcntatrc mites reinwardti Roemer, Sil. Fauna Westl. Tennessee, i860, 
p. 60, pi. 3, figs. 2a-c. — Pentremites {Troostocrinus) reinwardti Shumard, Trans. Acad. Sci. 
St. Louis, 2, 1866, pp. 384, 385. — Bassler, Bibliogr. Index, 1915, p. 1305; complete synonymy of 
genus and species. 
This species has been well known by weathered specimens in the Tennessee glades from 
the earliest times, but it is only with the present collections that its prolific occurrence in a 
definite horizon became manifest. Here in the middle zone of the Beech River shales it was 
obtained in place in large numbers, being so characteristic that the generic name was attached 
to that subdivision. It is probable that most of those from the glades were derived from 
erosion of the same bed. The species has a wide distribution throughout the Tennessee area, 
and has also been reported from the Louisville limestone of Kentucky. 
While specimens from the glades usually have the extremely narrow base broken off, 
the preservation of those found in the shales is excellent, presenting in a well defined type a 
considerable variation in size and proportions. I am figuring a representative selection rang- 
ing from, 10 to 45 mm. in height; and along with these a unique specimen with the brachioles 
intact — a condition not before seen. 
Horizon and locality. - Troostocrinus zone of the Beech River formation, Niagaran ; 
Tuck’s Mill and on glades in Decatur, WAyne and Perry counties, Tennessee. 
Troostocrinus sanctipaulensis Eoerste 
Plate 33, fig. 9 
Ohio Jour. Sci., 21, 1920, p. 64, pi. i, fig. 16. 
An imperfect specimen from the Laurel limestone at St. Paul ; differing but little from the 
preceding. 
Tetracystis fenestratus Schiichert 
Plate 33, figs. 10-14 
Echinoencrinites fenestratus Troost, Am. Jour. Sci., (2) 8, 1849, p. 419 (not defined) ; Bull. 64, U. S. Nat. 
Mus., 1909, p. 8. — Tetracystis fenestratus Schuchert, Smithsonian Misc. Coll., 47, 1904, p. 219, pi. 34, 
figs. 6-8. — Wood, Bull. 64, U. S. Nat. Mus., 1909, p. 8. — Bassler, Bibliogr. Index, 1915, p. 1263. 
This form was recognized by Troost in 1849, ai'id formed the subject of an elaborate 
description in his then unpublished monograph, as now appears in the U. S. National Museum 
Bulletin 64. In the meantime Schuchert’s description was published, based upon Troost’s 
solitary specimen, with proper credit to him. The species is quite rare, not having been found 
by any of the collectors since Troost and Roemer until the material now in hand was obtained 
in the Encalyptocrinus zone at the Tuck’s Mill excavations. This consists of eight specimens, 
of which I am figuring five, giving lateral views from four positions and one ventral. The 
circular cross-section of the calyx, the three abutting pairs of pectinirhombs, the four open 
ambulacral grooves traversing the surface longitudinally, are all thoroughly shown. The 
grooves were bordered by about ii pairs of brachioles marked by their slightly raised bases. 
TO 
