128 
SMITHSONIAN INSTITUTION 
Of Bather’s two American species we would naturally expect to find the prototype of our 
specimens in the one from St. Paul, P. long us; but the disparity in dimensions, and its extreme 
attenuation of form as indicated by its angle of only 38°, must clearly dififerentiate it ; while 
his Iowa species, closely approximate in size, with 28 grooves in symmetrical halves, and angle 
of 70°, seems to fit the case exactly. Therefore I am referring the three specimens confi- 
dently to P. inferior. 
The fourth specimen, not figured as it only shows the amorphous dorsal side, is much 
larger and more elongate than the others, being 45 mm., in length, with angle of 55°, prob- 
ably belongs to P. longus, but the absence of other characters makes comparison unsatisfactory. 
Horison and locality. Hopkinton and Laurel formations; Monticello, Iowa, and St. Paul, 
Indiana ; Dr. Foerste has also obtained a well marked specimen in the equivalent dolomite at 
Cedarville, Ohio. 
Family CROTALOCRINIDAE Angelin 
Genus CROTALOCRINUS Austin 
Plate 26 
Crotalocriniis Austin, Ann. Mag. Nat. Hist., vol. 10, 1842, p. 109. — Wachsmuth and .Springer, Rev. 
Pal., 3, 1886, p. 145; Proc. Acad. Nat. Sci. Phil., 1888, pp. 364-390, pis. 19, 20. — Bather, Treatise on 
Zool., pt. 3, 1900, p. 176. — Weller, Jour. GeoL, 10, 1902, p. 532. — Zittel-Eastman, Textb. Pal., 2d ed., 
1913, p. 216. — Bassler, Bibliogr. Index, vol. i, 1915, p. 292. 
While there is a certain analogy between this and the preceding genus 
owing to the fact that in both the arm-branches do not move independently as 
usual in crinoids, but are more or less connected laterally within the rays, upon 
which ground the two were thought by Weller when describing Petalocrinus 
to be closely related, there are also broad differences between them. Here the 
five rays, instead of being rigidly fused, have their many branches connected 
at short intervals so as to form a flexible network, in which the outlines of the 
brachials are plainly delineated on both dorsal and ventral surfaces ; these are 
connected laterally by points of attachment from near the middle of each ossicle, 
with open spaces between them, forming innumerable elongate meshes: owing 
to these lateral projections the brachials have the form of a cross with short 
arms ; they are long and flat on the dorsal surface, and deeply grooved for the 
ambulacra on the ventral. This pliant network is capable of considerable motion 
by way of folding and stretching, and in one species, C. pulcher, forms five 
broad, reticulate leaves which when closed over the calyx overlap one another ; 
and in another, C. rugosus, it is continuous for some distance around the calyx, 
and when spread out may be inrolled from the distal margin. 
In the formation of the calyx the two are also strongly different. Instead of having pen- 
tamerous symmetry as in Petalocrinus, the dorsal cup of Crotalocriniis is divided by an anal 
plate in line with the radials, after the manner of the Cyathocrinidae, and the infrabasals are 
large and prominent. In Petalocrinus the ray is articulated to the calyx by means of a single 
primibrach filling the entire radial facet, whereas in Crotalocriniis the lower brachials as far 
as the third or fourth order rest within the radial facet, and are more or less rigidly incor- 
porated into the dorsal cup by sutural connection among themselves, with the radials and 
with tegmen plates. It is only higher up in the rays, where the plates are no longer in contact 
