432 BULLETIN 12!), UNITED STATES NATIONAL MUSEUM 



Range. — From Cape Hatteras, North Carolina, via Gulf of Mexico 

 to Rio de Janeiro, Brazil. Bermuda. Shallow water to 30 fathoms. 

 Material examined. — See table, pages 434-437. 



MITHRAX (MITHRACULUS) RUBER (Stimpson) 



Plate 157 



Mithraculus ruber Stimpson, Bull. Mus. Comp. Zool., vol. 2, 1871, p. 118 

 (type-locality, reef at Cruz del Padre, Cuba; type not extant). 



Mithraculus nudus A. Milne Edwards, Crust. Reg. Mex., 1875, p. 110, 

 pi. 23, fig. 2 (type-locality, Guadeloupe; cotypes in Paris Mus.). 



Mithrax ruber Miers, Challenger Rept., Zool., vol. 17, 1886, p. 87. 



Mithrax nudus Miers, Challeyiger Rept., Zool., vol. 17, 1886, p. 87. 



Diagnosis. — Dorsal sulci shallow. Three antero-lateral protuber- 

 ances, all blunt in the old, the last one sharp in the immature. A 

 small lobe on outer margin of basal antennal joint. One lobe on 

 inner margin of arm. 



Description. — Carapace of moderate width; surface naked (pubes- 

 cent in the young), polished, and uneven. A few rounded promi- 

 nences are on branchial region; some small depressed tubercles are 

 arranged in transverse rows on gastric region, and larger ones occur 

 on cardiac and branchial regions. The lateral protuberances are 

 four, the first two blunt, the last two blunt in the old, sharp and 

 spiniform in the immature, the third largest and most produced, the 

 fourth postlateral; a tubercle on anterior slope of the second tooth, 

 a spine in the interval between second and third. Frontal horns 

 very short, thickened, upturned, blunt; interspace narrow, V-shaped. 

 Behind the horns two small acute prominences. Margin of orbit 

 thickened, especially the preorbital lobe; a small tooth on upper 

 margin; outer angle very slightly projecting. Basal antennal joint 

 rather narrow, with two lobes, one large and tliick at antero-external 

 angle and further advanced than preorbital lobe, the other small, 

 on outer margin. Chelipeds strong; arm with a single lobe at proxi- 

 mal end of anterior margin, four spines on posterior margin, and two 

 spines on upper surface; wrist almost smooth, its inner angle proxi- 

 mally situated and smoothly rounded. Hand with parallel margins; 

 immovable finger convex beneath; fingers denticulate except at base; 

 the movable finger in the full-grown male bears a strong tooth near 

 its proximal third; fingers gaping. Ambulatory legs spinous and 

 densely hairy, with fine and coarse hairs; merus of first three pairs 

 with a tubercle on lower margin. 



Color. — Carapace chestnut-red with some bluish posteriorly (Stimp- 

 son). 



Measurements. — Female (24096), entire length 13, width 15.8 mm. 

 The male type of nudus was much larger, 19 by 24 mm. 



Range. — From Cuba to Barbados and Cura9ao. 



