60 Trans. Acad. Sci. of St. Louis. 



length of the piece. Margins of the sinus drawn out to form 

 a prominent crest on both sides of the ambulacrum, thus 

 causing the interambulacral space to be slightly concave. 

 Deltoids small, the upper portion running out to a small 

 projecting spine. Summit openings, ^. e., mouth, anus and 

 genital openings, twelve in number and not confluent. 



This species, which resembles C. cormitus Meek and Wor- 

 then, differs from it, however, in the following characters : 

 The base is not depressed as much, the margins of the ambu- 

 lacral sini are less prominent, and the interambulacral spaces 

 are not excavated as much as in C. cormdus. The interam- 

 bulacra are twice as wide as in C . cornutus, in which species 

 the interambulacra are about as wide as the ambulacra. The 

 spiny projection is not as long or as prominent as in C. 

 cornutus. Besides the f oregoins: differences the surface orna- 

 mentation is different in the two species, being granular in 

 C. coriiutuSy and finely striated in the species under consider- 

 ation. 



Geological formation and locality : Subcarboniferous. 

 Divide between Koss Fork and Lincoln Valley, Montana. 

 The specimens were collected by Hay den's party, and first 

 mentioned in the Annual Report for 1872, page 470, un- 

 der the name Pentremites bradleyi. Meek. Types in the 

 Smithsonian Collection, numbered 24,529. By close exami- 

 nation it was found that the specimens under this number con- 

 sisted of two different species, one of these I have here named 

 in honor of mv friend, C. Schuchert. 



Saccoblastus vextricosus, n. s. 

 Plate IV., Fig. 7. 



Body bipyramidal. Base cup-shaped, with three charac- 

 teristic impressions peculiar to this genus. Articulation sur- 

 face of the column triangular. Column triansfular. Ambu- 

 lacrum very narrow, linear and sunk into the very prominent 

 ambulacral sinus. Interambulacrum smooth and dipping a 

 little toward the fork piece suture. Genital openings near 



