A CERA TA—MER OSTOMA TA. 411 



rounded anterolateral margins, and straight or slightly concave 

 anterior eyes, large, and near the front; body tapering in both 

 directions from third segment. 



Bertie waterlime of Buffalo, New York. 



XI. Pterygotus Agassiz. 

 Large, often gigantic Eurypterids, with a semiovate cephalo- 

 thorax, anterior marginal eyes and central ocelli ; the first pair 

 of cephalothoracic legs (preoral) very long and slender, terminat- 

 ing in large pincers or chelae, very probably prehensible in func- 

 tion; behind the mouth are four pairs of slender, walking legs 

 and behind these are the large swimming feet, which differ from 

 those of Eurypterus in being less broadly expanded at the ends; 

 telson an oval plate, either terminating in a short, projecting 

 point, or bilobed. Siluric-Devonic. 



24. P. macrophthalmus Hall. Siluric. 

 Cephalothorax subquadrate or tapering anteriorly ; eyes very 



large and high, with a circular base; chelae (pincers) with angular 

 front end; the posterior teeth on the larger division of the pincers 

 cire inclined and saw-like. 



Bertie waterlime of North Buffalo, New York. 



XII. EuRYPTERELLA Matthew. 

 Very small, elongated Eurypterids with small, triangular cepha- 

 lothorax; first four abdominal segments together subquadrate; 

 I)Osterior end tuberculated. Devonic (or Carbonic?). 



25. E. ornata Matthew. PDevonic or Carbonic. 

 Minute; length 8 mm., width 4 mm. Length of limb 4 mm. 



Segments increasing to the third one, then gradually decreasing; 

 a row of tubercles along the posterior margin. 



Little River Group ; plant bed No. 2, New Brunswick. 



XIIL Anthraconectes Meek and Worthen. 

 Differs from Eurypterus in absence of spines on the joints of 

 the cephalothoracic appendages, which terminate in single points, 

 in the great length and the simple extremity of the median appen- 

 dage of its operculum, and in the presence of two little spatulate 

 supplementary pieces. Carbonic. 



