508 Barbour — Carbonifero us Eurypterids of Nebraska. 



whorls closely imitate pale yellow flowers pressed in the shale. 

 The association of land plants with eurypterids has been 

 observed before. They suggest the probability that this group, 

 the sea scorpions, which originally were distinctly marine, had 

 undergone adaptive modifications suiting them to a brackish, 

 or even fresh-water habit. 



Intimately associated with the eurypterids were considerable 

 amounts of actual plant tissue, preserved as such since Car- 

 boniferous times. It still retains its pliability, can be stripped 

 from the shale, floated on glass slips, and made into permanent 

 mounts. There are now about one hundred of these mounts 

 in our collection. The preservation of actual plant tissue in 

 such amounts and in large pieces is quite unique. The tissue 

 is of a bright, transparent orange color. It is capable of close 

 study, and photomicrographic reproductions of the cell structure 

 a,re readily obtainable. This matter will be made the subject 

 of a special leaflet. 



As compared with well-known eurypterids, those of Nebraska 

 are small, the average being a trifle over two inches in length, 

 while the largest, as far as known, do not equal three inches. 

 Whether these represent adult or immature forms, is not ap- 

 parent. They may be immature forms. However, since no 

 evidences of larger individuals have presented themselves, it 

 may be that this is a group of diminutive eurypterids. Aver- 

 age eurypterids are five to ten times as large. The presump- 

 tion is that many of the specimens at hand are exuviae. 



The prominent feature of any eurypterid is its scorpioid out- 

 line. It has a broad flat head, two broad paddles, and a long- 

 segmented abdomen or body tapering towards the tail, which 

 usually ends in a sharp spiniform telson. The head-shield is 

 commonly semi-circular, or, in some instances, somewhat quad- 

 rate. It bears two prominent compound eyes, and certain 

 simple eyes, or ocelli, which are generally obscure. The head- 

 shield probably enabled Eurypterus to shovel and burrow as 

 does the horseshoe crab when in pursuit of marine worms. 

 The jawless mouth of Eurypterus is centrally located on the 

 ventral side of the cephalothorax, and is surrounded by six 

 pairs of appendages, some of the bases of which are so serrated, 

 spined, and dentated, as to serve functionally as jaws, or maxil- 

 lipedes. 



The appendages aside from the paddles are rather incon- 

 spicuous. The paddles are greatly enlarged for swimming, 

 and perhaps for roiling water to conceal and protect the 

 creature. The paddles are evidence, rather than proof, of 

 active swimming habits. In fact, Eurypterus may have been 

 rather sluggish, content perhaps with grovelling. Its life 

 habits may' be inferred from the closely related form, Limulus. 



