10 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



Systematic Discussion 

 Family PORCELLANIDAE 



Porcellaniens H. Milne Edwards, 1837, p. 246 (part; not Aeglea, 

 Megalops, Monolepis) (tribe). A. Milne Edwards and Bouvier, 

 1894, p. 245 (tribe). 



Porcellaniadae Randall, 1839, p. 136 (family). 



Porcellanidae White, 1847, p. 62 (family). Henderson, 1888, p. 104 



(family). Ortmann, 1892, p. 245 (family). 

 Porcellanidea de Haan, 1849, pp. xxii, 197, 199 (family). Dana, 1852, 



p. 400 (subtribe). 

 Porcellanodea Henderson, 1888, p. 103 (section). 

 Porcellaninea Holmes, 1900, p. 106 (legion). 



General form crablike. Carapace well calcified, depressed, regions 

 usually not well defined. Front often prominent, but never with a rostrum 

 greatly projecting beyond the eyes. Eyes pigmented. Antennae inserted 

 external to eyes, with three movable segments and a flagellum. Basal 

 segments of antennules broad, frequently touching on midline, their 

 anterior margins or faces often armed with spines or other projections; 

 remaining antennular segments short. Outer maxillipeds too large to be 

 contained in buccal cavity; ischium broad and flattened, merus broad, 

 flattened, with a prominent inner lobe, distal articles fringed with long 

 plumose hairs. Chelipeds moderately elongate, usually broad and de- 

 pressed; merus short, carpus usually elongate; nearly always a sharp 

 bend at articulation of carpus and manus, with latter directed inward. 

 Three well-developed pairs of walking legs; following pair feeble, 

 reduced in size, inflexed, and resting on the carapace. Abdomen broad, 

 symmetrical, composed of seven segments, bent under and closely ad- 

 pressed to thorax. Tail fan well developed, formed of the telson (segment 

 7) and the uropods of segment 6. Telson composed of five or seven well- 

 calcified pieces. Males with a pair of pleopods on segment 2; these 

 pleopods sometimes rudimentary or absent. Females with a pair of 

 pleopods on segments 3, 4, and 5 ; those on segment 3 sometimes reduced 

 or absent. 



Remarks: The limits of this well-defined taxon continue to be clear- 

 cut with increase in knowledge of the group. Its place in the general 

 scheme of crustacean classification and the rank to be accorded it were 

 matters of varying opinion among early workers; A. Milne Edwards 

 and Bouvier (1894) summarized the early history of its classification. 



