CRUSTACEA XORTII PACIFIC EXPLORING EXPEDITION I93 



naked, w ith a polished and elegantly colored surface. The carapax 

 is considerably longer than broad, with parallel sides. The gastric 

 lobules are not perceptible. The front is horizontal, continuous with 

 the upper surface of the carapax, laminiform, much projecting and 

 tridentate. The external antennc-e are similar to those of PorccUana 

 proper in the character of the basal joints. The scaphognath of the 

 external maxillipeds is dilated externally at the base, and attenuated 

 toward the extremity. The chelipeds are smooth, with unarmed 

 margins ; carpus very short : hand sufficiently elongated. The am- 

 bulatory feet are small, with a thick meros-joint and a short, com- 

 pressed multiunguiculate dactylus. 



These animals are parasitic in their habits, the armature of the 

 dactyli of the ambulatory feet enabling them to cling firmlv to the 

 zoophyte upon wdiich they live. This form of dactylus seems to be 

 indicative of a lower grade, being commonly seen in Galathca and 

 some Alacroura, but never seen among the Brachyura. 



The genus inhabits the warm eastern seas, in water of moderate 

 depth. 



301. PORCELLANELLA PICTA Stimpson 



Plate XXII. Fig. 6 



PorccllancUa ficfa Stimpson. Proc. Acad. Nat. Sci. Phila., .\, p. 24^ [81], 

 1858. 



Carapax oblong, depressed, smooth and even, glabrous, faintly 

 striated anteriorly and at the sides. Lateral margin scarcely acute, 

 but distinct, with the epimeral suture running close beneath it. Front 

 laminiform. tridentate. teeth acute, median tooth much larger and 

 more projecting than the lateral ones. Surface of the frontal region 

 transversely striated. External antennae more than twice as long as 

 the carapax ; coxal joint acutely prominent at its inner angle. 

 Epimera or latero-inferior regions of the carapax obliquely striated. 

 Chelipeds rather slender, sufficiently thick, somewhat rounded. 

 smooth, and glossy like the carapax ; anterior angles of ischium and 

 meros produced, acute ; carpus small, with smooth margins ; hand 

 elongated, contracted at the base, and ornamented within by a line 

 of pubescence extending longitudinally from between the bases of 

 the fingers to the middle of the palm ; fingers slender, tapering and 

 irregularly curved, as if distorted ; dactylus of larger hand much 

 shorter than the immovable finger. Ambulatory feet small, smooth, 

 glossy, almost naked ; inner edge of dactylus armed with four sharp 

 unguicles. the middle one largest. In the terminal joint of the abdo- 

 13 



