E. A. Andreics — Anatomy of the Spider Crab. 105 



tinually, baling out the water from the branchial cavity through 

 the efferent canal. 



The pair of appendages arising behind the second maxillje are the 

 first pair or ma.xillipeds (fig. 11). Eacii bears two smaller lobes {h,c) 

 near the median line : the innermost (c) which is much thickened, set 

 with stout setse, and projects forward from the side of the terminal 

 point of the sternal plastron to the posterior edge of the mouth ; and 

 two long somewhat united lobes {en^ ex), which run forward between 

 the mandible and the opening of the efferent canal. The outermost 

 of these latter lobes {ex) bears a slender palpus [p). 



Still farther from the median line, the maxilliped gives rise to a 

 long lamina {ep)^ which extends far back into the branchial cavity 

 over the surface of the branchiae and is called the epipodite or gill- 

 scraper (s, fig. 1). Its basal part is much broadened and lies under 

 the posterior half of the scaphognathite. 



In the next pair of appendages, the second maxillipeds (fig, 12), 

 the inner lobes (6, c) are less prominent, while the long external 

 lobes [ex, i-d) are entirely separate. The epipodite bears on its basal 

 stem-like portion a small, symmetrical branchia (br). This epipodite 

 extends below the branchioe, in the upper part of the branchial 

 cavity (s', fig. 1). 



The most posterior of the mouth ap])endages, the third maxilli. 

 peds (fig. 13) resemble the second maxillipeds; but the two long 

 lobes {ex, i-d) are much broader arid thicker, forming a stout covering 

 to all the preceding mouth parts. The long, stout stem of the epipo. 

 dite bears an unsymmetrical branchia {hr) and extends outward 

 above the basal joint of the chelate leg, forming a sort of valve to 

 the efterent opening of the branchial cavity, and then turns back 

 nearly at right angles, as a lamina, under the branchiae in the lower 

 part oi' the branchial cavity (s", fig. 1). 



The appendages of the head, which bear the sense organs, are the 

 pair of eye-stalks and the two pairs of antenna? or feelers. The most 

 anterior, the eye-stalks (fig. 14), are short, cylindrical, two-jointed 

 organs, arising side by side from the upper edge of the perpendicular 

 portion of the sternal wall and directed outward (e, fig. 1). The 

 basal joint {a, fig. 14) is imperfectly calcified on the posterior 

 side, but the second joint {b) is well calcified, constricted about the 

 middle, and terminates in a convex, transj)arent surface, serving as a 

 cornea (c). The entire appendage lies in the orbit, a cavity formed 

 by the union of processes of the rostrum and carapace with the basal 

 joint of the >:'econd antenna, and when not in use its corneal surface 



