202 Mr. R. I. Pocock on the Taxonomy 



if nnytliiiip:, further from tlie ^vaist tlian from the h>teral nnj^le, 

 snbpavalK'l to the area in front of it ; posterior prolongations 

 of opistiiosoma loss prominent, their inner edge convex and 

 cntting the outer at a right angle in the adult. Lateral crest 

 hor.lering the gill-chamber on the lower side of the oj)istho- 

 soina armed vith a strong spike; no transverse serrated crest 

 bordering the gill-chamber behind. 



Latiral movable spines on opisthosoma in female short, 

 abruptly narrowed and pointed at apex, not evenly tapering 

 to a |)oint. 



tSixth prMomiitic appendage with its fifth segment flat 

 behind, strongly compressed and much longer than the sixth 

 segment. 



No spine on inner edge of penultimate segments of endo- 

 podites ot branchial appendages of 0})isthosonia. 



Distribution. Oriental seas from the Bay of Bengal to the 

 coasts of China, Japan, the Moluccas, and Torres Strait. 



Genus Ty^CHYPLEUS, Leach, emend. 

 (PI. Y. figs. C, D, E, and PI. VL figs. 1, 2, 4.) 



Tdchypleus, Leacli, Diet, des Sci. Nat. xiv. p. 538 (1819); De^marest, 

 Cousid. G6n. Cruot. p. 350; Desiuarest iu Bosc, Man, Crust, ii. 

 p. 198 (1830). 



A movable spur present at apex of fourth segment of sixth 

 prosomatic appendage. Liner branches of genital operculum 

 not extending so far as tips of distal segments of the outer 

 branch. Postanal spine triangular in section, crested above, 

 hollowed below. Claspers of male heinichelate ; the immov- 

 able finger stumpy and abbreviated, the movable thick in the 

 middle, slender and cylindrical distally. Movable spines on 

 lateral border of opisthosoma very dissimilar in the two sexes, 

 of equal length and very long in the male and young female, 

 the posterior three short and apically acute in the adult 

 female. 



Tachypleus gigas (Miiller). 



? Lwiulus polyphemus, Fabr. Ent. Syst. ii. p. 488 (1793) (nee j)olt/- 



jilwmus, Liun., 17r4). 

 Limiilus yiyus, Miiller, Entoinostraca, p. 126 (1785) (in part.). 

 J^uti/pheiniig (/ir/iif, Laniarck, Syst. Anim. sans Vert. ed. 1, p. 168 (1801). 

 Limulus heteroductylus, Latn'ille, Hist. Nat. Crust, et Ins. iv. p. 89 



(1802) ; id. Souuini's Buffon, Ins. iv. p. 89 (1802) ; id. Gen. Crubt. 



et Ins. i. p. 12 (IbOti). 

 Litnului moluccanns, Latreille, Hist. Nat. Cruet, et Ins. iv. p. 92 (1802) ; 



id. Sonnini's BuHou, Ins. iv. p. 92 (1802) ; id. Gen. Crust, et Ins. i. 



p. 11 (180(5) ; Van der lioeven, Milne- Ed wards, &c. 

 Limulus Lafrei/lii, Leach. Diet, dee Sri. Nat. xiv. p. 527 (1819). 

 Tiichypleue hetervdactijlus, Desmarest, Cjntid. g6n. Crust, p. 300 (1825). 



