Cwmerate Crinoids. — Wachsmuth and Springer. 137 
open grooves, of which the covering-pieces were not preserved. 
These grooves, as they pass out from the orals, bend at first 
slightly downward, but after bifurcating proceed upwards to the 
arms. Nothing is known of the structure of arms and column. 
Horizon and Locality: Upper part of Niagara group ; St. Paul, 
Shelby Co., Ind. 
Type in the collection of Wachsmuth and Springer. 
Idiocrinus ventricosus W. and Sp. (nov. spec.) 
A very small species. Calyx nearly as wide as high; hight 
of dorsal cup about equal to that of the tegmen; the former 
bowl-shaped, the cup obtusely pyramidal. Plates smooth; the 
radials and costals somewhat longitudinally convex, causing a 
depression of the intcrbrachial spaces. Suture lines slightly 
grooved. 
Infrabasals extremely small and covered completely by the 
column ; placed at the bottom of a narrow circular cavity, formed 
by the lower ends of the basals. Basals of moderate size, their 
lower ends incurving and forming the sides of the concavity, 
their upper angles slightly bending upwards. Radials once and 
a half as large as the two costals together, and twice as wide as- 
high; three of them heptagonal, the two posterior ones hexa- 
gonal. First costals quadrangular, much narrower than the radi- 
als, and three times as wide as high; the second of nearly the 
same width as the first but longer. Distichals narrower and 
shorter than the second costals. Interbrachials large, subellip- 
tical ; that of the anal side a little wider, and truncating slightly 
the posterior basal. Oral pyramid convex, a very little tumid,, 
extremely large for the size of the species, perfectly closed at the 
summit, and the interoral sutures obsolete. The outer face of 
the pyramid is covered with well defined radiating ridges, which 
proceed from the middle of the plate to the outer margins, in- 
creasing in hight and width as they pass outward. Ten of these- 
ridges are more prominent, and project outward around the cir- 
cumference, so as to give to the plate the aspect of a ten-rayed 
star. The inner floor is excavated centrally, and there are five 
deep grooves passing out in a radial direction. The interam- 
bulacral plates long, slender and cuneate, attached with their 
narrower upper ends to the inner margin of the orals. They 
project outward so as to form at their sides open spaces for the 
reception of the ambulacra. Other parts unknown. 
