WATERLIME GROUP. 41»* 



This is the only carapace which I have seen, where the eyes are marginal. In the 

 form and appearance of the carapace, the specimen resembles others of the genus; 

 but I am not aware that the central tubercle, with the eye-like spots, has been 

 noticed in Pterygotus. A similar feature has been observed in Eurypterus, though 

 not seen in all the species of the genus. 



Fig. 8. The carapace, natural size. 



Fig. 8 a. A small portion enlarged, to show more distinctly the oblong tuhercle, and the 

 small eye-liie points which are faintly visible to the naked eye. 



Geological position and locality. In the Waterlime group : Wheelock's hill, 

 Litchfield, Herkimer county. 



Pterjgotus osborni ( n. s.). 



Platk LXXX a. Fig. 9. 

 Cakapace unknown. Body elongate. The four anterior joints of the thorax 

 have a width of about four times their length. The first segment shows 

 the point of attachment for the thoracic appendage, as in Eurypterus. 

 Postoral plate elongato-cordiform. First joints of the natatory feet 

 rhomboid-ovate, and toothed on their inner margins ; the four anterior 

 feet slender, with long joints ; the basal joints broad, with long spine- 

 like teeth. The entire length of the cephalic portions, and the four first 

 joints of the body, is about three inches. 



Fig. 9. A figure of the specimen, natural size. A reference to the parts of Eurypterus will 

 explain the relations of the parts of this figure. 



Geological position and locality. In the Waterlime group : Waterville, Oneida 

 county. 



CERATIOCARIS. 



The posterior or caudal spines of this crustacean have been known in our 

 rocks from fragments in the Clinton and Niagara groups, as well as in the 

 Waterlime group. Until their true character was pointed out by Professor 

 M'CoY of London, these fossils were regarded as the defensive spines of 

 fishes, and were thus described. A species from the Niagara group has 

 been described in the second volume of the Paleontology of New- York, 



