106 E. A. Andrews — Anatomy of the Spider Crah. 



is concealed by being folded back against the concave surface of the 

 process arising from the carapace, as at e, fig. 20. 



The first pair of antennae, or antennules (fig. 15), are inserted 

 immediately below the eye-stalks, but are directed downward and 

 forward. They lie in the antennulary cavity, which is bounded 

 below by the basal joint of the antenna on either side, and is roofed 

 over above by the rostrum. The large cuboidal basal joints (a) 

 nearly fill the upper part of the cavity, and are separated from one 

 another by a median partition formed by a process of the rostrum 

 and one from the epistoma or antennary sternum. Three joints beav, 

 on the side farthest from the median line, a slight groove (A) marking 

 the entrance to the auditory sac or ear. The remaining joints of the 

 antennule may also be folded up within the cavity and thus protected. 

 The second (i) and third (c) are more slender than the first, and cyl- 

 indrical; the third bears at its extremity two short, jointed filaments 

 ( /■, (j). The lower or posterior filament {g) is composed of about 

 nine joints ; the anterior (/), of about twenty-nine, which, except 

 the large basal one and the terminal three, are very short and bear 

 on their lower sides light colored seta with dark brown bases, 

 forming a dense brush. 



The second antenna, or antennae proper (fig. 16), arise below and 

 exterior to the antennuliK and project forward horizontally («, fig. l). 

 Tlie basal joints («, fig. 16) are very large, rectangular in outline, 

 and are firmly soldered at their bases to the antennary sternum. and at 

 their tips to the rostrum, thus bridging over the passages joining the 

 orbits with the antennulary cavity. Near the base of each, is the 

 opening of the duct of the green gland, which is closed by an ellip- 

 tical plate {a, fig. 16), produced within the body cavity as a slender, 

 chitinous process. The two following joints of the antenn:>? {li) are 

 much smaller than the first, resembling the corresponding joints of 

 the antennuhe, and lie by the edge of the rostrum. From the eX; 

 tremity of the third joint a single slender filament (<7), composed of 

 about fifteen joints, projects forward a little beyond the tij) of the 

 rostrum (fig. 1). 



Alimentary System. — The alimentary canal (fig. 19) includes the 

 (esophagus, stomach, and intestines, with their appendages. 



The mouth is a longitudinal, quadrangular opening at the center 

 of the peristome, bounded anteriorly by the large fiesliy lobe, the 

 labnim (/6, fig. 1 9), laterally by the mandibles, and posteriorly by 

 the forked metastoma, a lobe of wliidi lies in the cavity on the pos- 

 terior face of each m.-nulible. 



