CLxVSS II 



ARACHNIDA— EUKYPTERIDA 



783 



Tyloptcriis Clurke and Ruedemann. Thick calcareo-chitinous integument, 

 witli median divided knobs on tergites. Silurian ; Canada. Type, Eurypterus 

 hoylei Whiteaves. 



Echinognathns Walcott. Imperfectly known. Cephalothoracic appendages 

 with numerous curved spines, indicating an animal of large size. Ordovician ; 

 New York. 



Megalograptus Miller. Richmond beds (Lowermost Silurian) ; Ohio. 

 Known only by fragmentary remains. 



Dolichoptenis Hall. Sixth prosomatic appendage has the terminal claw 

 developed into an elliptical oar-plate. Waterlime (Upper- 

 most Silurian) ; New York. Silurian ; Oesel. 



Eusarcus Grote and Pitt (Eurysoma and Carcinosoma 

 Claypole). Eurypterids with the six mesosomatic Seg- 

 ments greatly expanded, the next following of the 

 metasoma being abruptly contracted. Prosoma subtri- 

 angular, Compound eyes at apex in front ; metastoma 

 subtriangular. Second pair of legs the longest. Terminal 

 Joint of the sixth prosomatic appendage not expanded. 

 General aspect of body scorpion-like. Ordovician and 

 Silurian ; New York, Indiana, and Pentland Hills, Scot- 

 land. 



Anthraconedes Meek and Worthen. Like Eurypterus^ 

 but with spines on the falcate posterior angles of the 

 abdominal segments. Goal Measures ; Illinois and 

 Pennsylvania. 



Adelophthalmus Jordan and von Meyer. Comprises 

 eyeless Eurypterids. Goal Measures ; Saarbrücken. 



? Eurypterella Matthew. Probably not a Eurypterid. 

 Devonian ; New Brunswick. 



? Beitina Walcott. Probably not a Eurypterid. 

 Algonkian ; Montana. 



Slimonia Page (Himantopterus Salter) (Fig. 1509). 

 Body attaining a length of 60 cm., and width of 15 cm. 

 Prosoma subquadrate, with anterior marginal eyes and 

 median ocelli. Preoral appendages in the form of small shlrr"scoSid"'Rts"toia- 

 stout pincers, much like chelicerae in Limulus. Of the tion ' of ventral aspect, 

 five pairs of postoral appendages, the first is modified to Le^msoma^i?— vl^ViS- 



tal operculum VII.— VIII., 



Segments of the mesosonia 



The first two sternites vii- - xii metasoma 



. . XIII.— XVIII., and telson 



are represented by the genital plate and its posterior xix. Dotted areas of the 



j. . • i.t, J.I, ü j' ^' 1 j. 1 • mesosoma are branchial 



divisions ; the other nve are discontinuous plates bearing lameiiae .showhig tiirough 

 branchial lameiiae on their inner surface. The five f)^%£'Srier'"'^^^^°'' 

 posterior segments are long, narrow, and cylindrical. 

 Telson like that of Pterygotus, but produced into a longer spine. Only one 

 species known. Old Red Sandstone ; Scotland. 



Stylonurus Pa,ge (Fig. 1510). Body similar in general proportions to 

 Pterygotus, and often exceeding 1 m. in length. Prosoma quadrate or sub- 

 pentagonal, its margins bent under. Eyes large, approximate, sometimes 

 supported by strong orbital ridges ; ocelli on the slope of a median ridge. 

 Preoral appendages chelicerate. The five pairs of postoral appendages 



Fig. 1509. 

 Slimonia acuminata 



form tactile organs. The first seven postcephalic seg- äinnent8"of"the^ 

 ments much wider than the rest. 



