CRUSTACEA NORTH PACIFIC EXPLORING EXPEDITION 9 



-on bottoms more or less muddy. In a living state it was of a light 

 brick-red color above, often iridescent ; below yellowish-white ; sides 

 of feet shining white. The posterior feet are short. The dimen- 

 sions of the carapax of a large female are: Length, 2.57; breadth, 

 '2.'j2 inches. 



In Gerstgecker's figure the surface of the carapax posteriorly and 

 the upper sides of the ambulatory feet are represented as much more 

 rugose than in any of our specimens. 



Chionoccclcs is evidently nearest allied to Hyas, although probably 

 .a higher form. In young specimens the resemblance to Hyas is 

 ■easily noticed. Hyas chilensis should probably belong to it. It has 

 considerable resemblance in general appearance to Salacia of the 

 opposite extremity of the American continent, of which it may be 

 •considered the analogue. 



Genus HYAS Leach 

 5. HYAS LATIFRONS' Stimpson 



Plate II. 



Hyas coarctatus Stimpson (non Leach), Crust, and Echin. of the Pacific 

 shores of N. America, Jour. Bost. Soc. Nat. Hist., vi, p. 450, 1857. 



This species differs from H. coarctatus, of the North Atlantic, in 

 the following characters, which are found to be constant upon exam- 

 ination of numerous specimens of both forms : The body is thicker 

 ■and much broader anteriorly across the post-orbital apophyses ; the 

 angles are all more obtuse. The dorsal surface is marked with 

 fewer tubercles, which are also much larger and more obtuse, most 

 ■of them being rather swellings than warts. The rostrum is shorter 

 and less acute ; and the superior fissure of the orbit is always closed, 

 its margins overlapping. 



It is subject to considerable variation in some of its characters, 

 ■particularly in the greater or less approximation of the forks of the 

 rostrum, which may be so closely appressed against each other as to 

 overlap, or may diverge so as to leave a narrow V-shaped space be- 

 tween. They diverge most in the young. The feet and inferior 

 surface of the body are densely hirsute in some individuals and quite 

 smooth in others. The color is a dusky brick-red above, whitish 

 below. The dimensions of a male from the Arctic Ocean north of 

 Bering Strait are: Length of carapax, 2.85; greatest breadth, 2.12; 



^ Hyas coarctatus Leach. 



