90 



and hence only part of it can be described. Tlie pseudoambulacra 

 are very narrow and thei'e are only five hydrospire slits in an 

 area. 



This species is distinguished by its general form and smooth 

 surface. The depressed sutures between the basals is a distin- 

 guishing feature, and so are the tive hydrospire slits in an area. 



Found by Miss Jessie Blair, in the Choteau limestone, at Se- 

 dalia, Missouri, and now in the collection of S. A. Miller. The 

 specific name is given as a compliment to the finder. 



CLASS CRUSTACEA. 



SUB CLASS XIPHOSURA. 



ORDER EURYPTERIDA. 



Family EURYPTERIDA 



EURYPTERCS KOKOMOENSIS, U. Sp. 



Plate V, Fig. 1. the lower or ventral side of a nearly complete 



specimen. 



This species seems to be about the size of Enrypterus remipes, 

 but differing somewhat in the relative proportions of the body. 

 The carapace is roundish or somewhat quadrangular with tbe an- 

 terior corners rounded and about seven-eighths as long as wide. 

 The abdomen gradually widens from the carapace for three or 

 four articulations and then contracts gradually to the last segment, 

 or it may be said to be somewhat evenly rounded laterally. The 

 posterior projections or angles of the segments are only partially 

 preserved in our specimen, until the last segment is reached, and 

 here they appear much larger than is usual, in this genus. There 

 are twelve segments. Telson tapers slowly to near the end when 

 it rapidly tapers to the point. The length of the telson is about 

 two-nintlis of the entire length of the animal. 



There are only two pair of the palpi preserved, in our specimen, 

 and they appsar, as shown in the illustration. The limestone rock 

 is disposed in thin layers and others may have been broken away 

 without leaving a trace of their former existence. The pair of 

 swimming feet are unusually large, but the specimen preserves 

 little more than a bare outline of them. The mouth too is in- 

 distinct but the outline of the small post oral plate is preserved. 



