PLATYCRINTDAE 
59 
Arms stout, two to the ray, with pinnule openings between their bases some- 
times seen. Tegmen low conical, abruptly constricted above the arm-bases, and 
distinctly narrower than the cup ; plates flat or low convex, smooth or studded 
with small tubercles; ambulacra not conspicuous. Surface of cup ornate, usually 
corrugate, sometimes with ridges forming striae, or lines parallel to margin 
of plates ; sutures often sharply beveled. 
A well marked species, usually readily recognized by the high calyx, large basal pen- 
tagon, and a certain massiveness not apparent in most other species. The constricted tegmen 
is very decisive, but this is seldom preserved, and with only the dorsal cup the large pentagon 
and vertical sides are usually sufficient. In well preserved specimens the sculpturing is highly 
ornate. This is clearly the form described l.iy Troost under the names C. striafiis and C. in- 
flatus, as shown by his type of the latter, and the figures of the former in the monograph of 
1909, pi. 9, figs. 13, 14. The first name being preoccupied by Wachsmuth and Springer, the 
last should stand for the species. A specimen of it was figured by us as M. tennessecnsis 
(N. A. Crin. Cam., 1897, pi. 75, fig. 17 only). 
The enlarged details of a specimen of this species shown by figure 8 of plate 15, along 
with another which may he of M. rosacformis, are reproduced from my works on ScypJw- 
cnnus, 1917, pp. 33-38, pi. 9, figs. 5a-c, and Dolatocrinus, Bull. 115, U. S. Nat. Mus., 1921, 
p. 24, pi. 2, figs. 3, 4. They were given for demonstrating the true nature and function of 
the interbrachial apertures observed in various genera of the Camerata, and frequently desig- 
nated as “ respiratory pores,” which are now seen to be the openings for pinnules, the ambu- 
lacra leading to which are shown in some specimens of other species. For a full discussion 
of this subject, and the significance of these specimens, reference should he had to those 
papers, at the pages indicated. 
Horizon and locality. Beech River formation, chiefly Encalyptocrinus zone, Browmsport 
group, Niagaran ; Tuck’s Mill and glades, Decatur County, Tennessee. 
Marsipocrinus verneuili (Troost) 
• Plate 16, figs. 1-6 
Cupellaccriuites verneuili Troost, Proc. Am. Assn. Adv. Sci., 1850, p. 61 (nom. mid .). — Marsipoerinus 
verneuili (Troost), Wood, Bull. 64, U. S. Nat. Mus., 1909, p. 32, pi. 9, figs. 10, ii, 12. 
A small species, average diameter of calyx about 15 mm. Calyx bi-convex, 
with shallow concave base, beigbt to width about as i to 2. Basal pentagon about 
half the total diameter, broadly excavate, bounded by a conspicuous, obtusely 
triangular rim, much larger than the column-facet, flaring outward to a sharp 
edge. iBr not projecting, bent over into the tegmen. Arms tapering, two to the 
ray. Tegmen lower than cup, with low, smoothly rounded plates: ambulacra 
narrow, well defined, with some outer divisions running to pinnule openings. 
Surface of cup coarse striato-corrugate or rugose. 
This species as represented hy Troost’s type is well defined, and is confirmed by seven 
specimens in the present collection. The flaring rim around the column is a striking character, 
seen to some extent in other species, but in none so conspicuous as this. 
Horizon and locality. Beech River formation of Brownspcrt group. Encalyptocrinus 
zone, Niagaran; Tuck’s Mill, Decatur County, Tennessee. 
