Measurements. — Carapace: large male, length, 

 36 mm., width, 43 mm. ; ovigerous female, length, 

 16 mm., width, 19 mm. 



Variations. — In young individuals the rostral 

 horns are wider behind and flatter than in adults ; 

 the notch between the rostral horns in extremely 

 large individuals may be U-shaped; the large 

 tubercle above the posterolateral margin may be 

 spiniform but is located higher on the carapace 

 than the similarly formed tubercle in M. hispidus. 



Color. — Carapace yellowish white, with blotches 

 of bright red ; two largest red spots over branchial 

 areas, a median spot on cardiac area, a pair situ- 

 ated farther back, a small pair behind orbits, and 

 another beneath orbits; legs yellowish white, 

 blotched or barred with red ; chelae light red with 

 pale tips (Verrill, 1908, for M. depressus) . 



Habitat. — This species, which is often encrusted 

 with bryozoans and other organisms, is found 

 predominantly on coarse or rocky substrates but 

 occasionally on muddy or sandy bottom. In North 

 Carolina it is a common species on the offshore 

 banks and is associated with Mithrax forceps. 

 Pearse (1934) found the species in canals of the 

 sponge Stematumenia strobilinia (Lamarck) at 

 Tortugas, Fla. Shallow water to 28 fathoms. 



Type localities. — Key "West, 2-5 fathoms, Tor- 

 tugas, 5-6 fathoms [Fla.] ; St. Thomas. 



Known range. — Beaufort, N.C., to Pensacola, 

 Fla.: Yucatan Channel off Cape Catoche, Mexico, 

 and Gulf of Campeche; West Indies to Venezuela; 

 Bermuda. 



Remarks. — Ovigerous females are known in 

 Florida from December to February, and in 

 August. They are known from North Carolina 

 in April, St. Thomas in July, and Venezuela in 

 September (Rathbun, 1925; U.S. National Mu- 

 seum records). 



Mithrax (Mithraculus) forceps (Milne Edwards) 



Figures 238, 245E 



Mithraculus forceps Milne Edwards, 1875, p. 109, pi. 23, fig. 1. 

 Mithrax forceps: Hay and shore, 1918, p. 457, pi. :>s, tig. l. — 

 Rathbun, 1925. p. 431, pi. 156 (rev.). 



Recognition characters. — Carapace about one- 

 fifth wider than long, deeply sculptured in young 

 individuals but smoother with age. Anterolateral 

 margin with four tubercles or teeth exclusive of 

 postorbital angle, separated by broad rounded 

 sinuses, first tooth usually shortest, remainder 

 usually acute and turned forward at tip. Three 



Figure 238. — Mithrax (Mithraculus) forceps (Milne 

 Edwards). Male in dorsal view, legs of left side not 

 shown, 5 mm. indicated. 



grooves running diagonally backward over bran- 

 chial area from near first, second, and fourth 

 sinuses of anterolateral margin, between these 

 grooves two well-defined, unbroken ridges and a 

 broken ridge behind third groove. Cardiac and 

 gastric regions crossed by less sharply defined 

 ridges somewdiat broken up into low rounded 

 tubercles. Notch between rounded rostral horns 

 broadly V-shaped, two pairs of tubercles on 

 frontal region behind lobes of rostrum. Preorbital 

 angle prominent, not exceeding rostrum. Orbital 

 margin with a dorsal and ventral tubercle near 

 postorbital angle. Outer spine of fused antennal 

 article nearly equaling rostrum. 



Chelipeds strong. Merus with two strong spines 

 or tubercles in front, five much smaller ones on 

 posterior margin, and usually two on upper sur- 

 face near posterior margin. Carpus smooth or 

 with a small spine or tubercle on inner margin 

 near inner distal angle. Hand smooth, polished, 

 somewhat tumid. Fingers widely gaping in male, 

 with expanded hollowed-out tips: dactyl with 

 single large tooth one-third distance from proxi- 

 mal end, or with a few minute teeth: immovable 

 linger with from one to three small teeth or tuber- 

 cles in middle. Walking legs spiny or denticulate 

 with many fine hairs. 



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