SECT. XIV THE EURYPTERID/E 243 



highly sensitive antennae, has larger rowing limbs in 

 proportion to the size of the body than Pterygotus 

 (Fig. 55), which does not seem to be so well provided 

 with such organs. The latter animal moved more slowly 

 and caught its prey with its powerful pincers. The 

 former darted forward with great rapidity and caught 

 its prey at once between its numerous jaws. 



We consider then the Xiphosurid^e as early Trilobites 

 specialised for slow deliberate browsing ; the Eury- 

 pteridai on the contrary for a rapid darting method of 

 capturing prey. That the Trilobites did employ the 

 springing movement which we have here assumed 

 purely on morphological and biological grounds, has 

 been lately confirmed by the discovery of a Trilobite 

 track, which, according to Ringueberg the discoverer, 

 could only have been produced by a series of 

 jumps.^ 



This description of the manner of life of these 

 animals (the Eurypteridse) renders it not so necessary 

 to describe the limbs of the two animals ; still, as there 

 are points of great interest in their morphology, a 

 short account of them will not be out of place. 



Taking Pterygotus first, we have the first antennae 

 developed into long chelate seizing feet, like the first 

 antennae of Limulus, but much more highly developed. 

 The analogy of the Scorpionida^ will at once suggest 

 itself, where for the same purpose the palps have 

 developed in the same wa}^ These chelae of Ptery- 

 gotus were probably richly provided with sensors- 

 hairs, since the limb on which they were developed 



^ Proc. American Association, 1886. 



R 2 



