WATERLIME GROUP. 423* 



Fig. 10. The posterior joint of the body and tail-spines. 

 Geological position and locality. In the Waterlime group at Waterville. 



For the means of making these examinations and comparisons of nume- 

 rous specimens of the different species of Edrypterus, I have been 

 indebted to several gentlemen for the loan of specimens from their 

 private collections. 



Some years since, Mr. Osborne of Waterville presented me with a small 

 collection of specimens of Eurypterus remipes, the study of which has 

 revealed some interesting points in the structure of these fossils. 



To Col. E. Jewett, I am indebted for the use of several interesting 

 specimens. The State Collection has furnished the only illustration of 

 Eurypterus dekayi, and the principal illustration of E. pachycheirus and 

 some others. The very fine collection of Mr. C. Cobb of Buffalo has sup- 

 plied means of illustration for E. lacustris and others, and also for the 

 peculiar form Dolichopterus ( Plates Lxxxiii and lxxxiii a). To the same 

 collection I am also indebted for the large fragment of Pterygotus, and 

 some illustrations of Ceratiocaris. 



I regret extremely that I could not have had the means of exploration, 

 in the strata from which these specimens were obtained ; for great as is 

 the advance made in our knowledge of these interesting fossils to the 

 present time, there is yet much to be done in bringing to light more 

 perfect individuals of the forms already known, and of adding new species. 



The facts deduced from the observations I have been able to make, 

 indicate that these animals were restricted in their geographical distribu- 

 tion ; that they congregated in large numbers in the localities where we 

 find them, or at least that their remains indicate the existence of large 

 numbers of individuals in proximity to the localities where they occur ; 

 though it is probable that many specimens, particularly of dismembered 

 parts, were the cast-off coverings of living animals. 



