MILWAUKEE CR I NO IDS. 123 



highly elevated into a conspicuous node-like projection. Deltoid 

 plates, with the exception of the posterior one, apical, not visible 

 in a side view. Posterior deltoid small, rhomboidal, not well 

 preserved in the specimen. 



Ambulacra linear, narrow, narrowly rounded at the base and 

 about one-half as wide at that point as at the summit. Surface 

 transversely convex, forming a longitudinal depression along 

 each side, the central portion raised not quite to the general 

 level of the radials. The food groove in the center of each 

 ambulacrum deepens and broadens near the summit. 



Spiracles five, rather large, the posterior one confluent with 

 the anal opening. The remaining characters of the summit not 

 well preserved. 



Surface of the radials ornamented with fine concentric lines 

 which are only visible with a lens. 



Remarks. The species here figured and described is with 

 some hesitation identified with Whiteaves P. filosa. It differs 

 from that species in its greater proportionate height, the pro- 

 portions between the width and height in Whiteaves' figure being 

 3 to 4, while in the Milwaukee species it is 3 to 5 ; in the 

 higher and more slender basal cup, and in its more con- 

 spicuous node-like projections of the radials at the basal margin 

 of the sinus. So far as the Milwaukee specimens have been ob- 

 served, they are always smaller than Whiteaves' figures. 



Pentremitidea milwaukensis n. sp. 

 (PL XIV. Fig. 5.) 



Body of medium size, lateral outline subovate, maximum 

 breadth a little below the middle 6f the radial sinuses. Cross- 

 section at the point of maximum width decagonal, the sides ot 

 the decagon represented by the ambulacral areas, short and con- 

 cave, the other sides longer, nearly straight or slightly concave. 



Basal plates three, two pentagonal and larger than the third, 

 which is quadrangular, less than one fifth as high as the radials. 

 Basal cup trihedral, wider than high. Radials lanceolate in out- 

 line, a little more than twice as high as wide ; the bodies or un- 



