DIMEROCRINIDAE 
17 
a cavity forming an inverted cone with the small IBB at the bottom. RR very 
large. iBr and IIBr projecting over into the tegmen, hut exteriorly the brachials 
pass insensibly into the large biserial arms, two to the ray, which abut closely 
both between the rays and their divisions. Ventral pyramid somewhat variable 
in shape, asymmetric, consisting of five similar plates with a smaller central one 
interposed ; or the central plate may represent the posterior oral pushed in be- 
tween the others by anal structures, with the posterior triangular plate flanked 
by two others connecting forming the border of the anal opening. These pyramid 
plates abut by their proximal edges upon the bent over processes formed by ex- 
tensions of the IIBr and iBr plates. Surface smooth. 
Horizon and locality. Laurel limestone, Niagaran ; St. Paul, Indiana. 
Gazacrinus magnus new species 
Plate 2, figs. 10, ii, 12 
This species, from the same horizon and locality as the preceding, is known 
only from the tegminal pyramid, which is of great size, and exhibits in a re- 
markable degree the sharp ridges — 5 or 10 in number — forming the border of 
vertical grooves or compartments in which the arms may rest as in Eitcalyfi- 
tocrimis. There are 3 specimens. Fig. 12 has only 5 broad grooves, while 
fig. 10 has 10, with extremely sharp dividing ridges. This pyramid is formed 
by the sutural union of 5 elongate plates, as is clearly shown by the interior view 
of the same specimen in fig. loa. This is further confirmed by fig. ii, which 
shows a single detached plate of a similar and larger pyramid. Here there is no 
question of a central plate as in the preceding species. 
Horizon and locality, same as last. 
Gazacrinus depressus new species 
Plate 2, figs, ig, 14 
A crushed specimen from St. Paul of different type from the preceding, 
rather resembling the Tennessee form. 
Horizon and locality, same as last. 
Gazacrinus ventricosus (Wachsmuth and Springer) 
Plate 2, figs. 15-16 
Idiocrimis ventricosus Wachsmuth and Springer, Am. Geol., lo, p. 137; N. A. Crin. Cam., 1897. p. 205, 
pi. 18, figs. 9 a-b. 
Specimens very small, height to width at top of IIBr about 2 by 2.5 mm. 
Calyx low, subglobose, but with base excavate and IBB sunken in the cavity. 
iBr large, elongate, projecting inward where their extensions support the teg- 
minal pyramid, which here consists usually of anchylosed plates by the fusion 
