REPORT OF THE STATE PALEONTOLOGIST 1902 1091 



areas which in the female Eurypterus lie in front, one on 

 either side of the median suture. The parts of the genital 

 appendages correspond in a general way to those of Eurypterus, 

 though there is considerable difference in their form. In the 

 female the appendage consists of two parts, one carried by the 

 operculum, the other by the following sternite. The part car- 

 ried by the operculum is slender with a sagittate base, and is 

 divided transversely into two portions, but lacks the pair of 

 short, flat, diverging, terminal crura. That carried by the sec- 

 ond sternite is simple, broader at the base and attenuated at 

 the distal end, instead of having articulated to it, two diverging, 

 ensiform strips (14). In the male, as in Eurypterus, the ap- 

 pendage is confined to the operculum, and is shorter and broader 

 than that of the female; but is proportionately larger than in 

 that genus. 



The genus Slimonia is suggested in three ways: by the mar- 

 ginal position of the compound eyes, by the shortness and 

 edentulous character of the masticatory preoral appendages, 

 which are, however, less robust in that genus, and by the length 

 of the telson and the slight indication of inflation in the an- 

 terior portion. In other respects there appears to be consider- 

 able difference between these genera. 



From a consideration of the foregoing facts, it appears that 

 Hughmilleria is most closely related to Pterygotus. With 

 Pterygotus and Slimonia, it makes three genera of eurypterids 

 having the compound eyes marginal. In development of preoral 

 appendages, it comes between Pterygotus and the other genera 

 in which these appendages are known, including Eurypterus, 

 Dolichopterus, Stylonurus, Eusarcus and Slimonia. 



Hughmilleria socialis sp. nov. 



Plates 6-9; 10, fig. 1-6, 8-9; 11-14; 15, fig. 4-6; 24, fig. 1; 25, fig. 1 ,3, 4; 26, fig. 3, 5 



This type is comparatively small, the length of the average 

 individual not exceeding 15 cm. Viewed from either the dorsal 

 or the ventral side, the outline is slenderly lanceolate. In the 

 natural, undistorted condition, the anterior part of the body 

 is flattened, the dorsal and ventral surfaces being slightly con- 

 vex, while the caudal portion is nearly cylindric. 



