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THE SPIDER CRABS OF AMERICA 417 



MITHRAX (MITHRAX) TORTUGAE Rathbun 



Plate 147, fig. 2 



Mithrax (ortugae Rathbun, Proc. Biol. Soc. Washington, 

 vol. 33, 1920, p. 23 (type-locality, Tortugas; type. 

 Cat. No. 50442, U.S.N.M.). 



Diagnosis. — No spine nor tuborcle on postcro-lat- 

 eral margin, but a tubercle above the margin. 

 Rostral sinus V-shaped, horns very wide. Two 

 tubercles or blunt spines on anterior margin of arm. 



Description. — Carapace wider than in the three 

 preceding species; the marginal hepatic and the 

 prominent first branchial lobe rectangular, their an- 

 terior margins transverse, their posterior margins 

 longitudinal, the branchial lobe having a very short 

 hooked spine at the angle. Second branchial lobe 

 or spine low, conical; third spine slender, hooked; 

 from it a line of two tubercles runs obliquely trans- 

 versely backward on the carapace. No spine nor 

 tubercle on the true postero-lateral margin. Rostral 

 horns short, broad, sub truncate; sinus V-shaped. 



Two blunt spines or tubercles on anterior or inner 

 margin of arm, the distal one larger. Tubercles of 

 wrist very low. 



Otherwise as in M. pleuracanthus which it most 

 nearly resembles. 



Color. — A specimen preserved in formalin has reg- 

 ular patches on the carapace which are finely dot- 

 ted with dull crimson. Chelipeds closely spotted 

 and finely mottled with the same. Merus of legs 

 incompletely banded with a brighter crimson, with 

 some small spots of the same shade on the succeed- 

 ing segments especially at articulations. 



Measurements. — -Female, holotype, total length of 

 carapace 19.7, width without spines 22.1, with 

 spines 24.3 mm. 



Range. — Bahamas; Plorida Keys; Curasao. 



Material examined. — 



Abaco Island, Bahamas; 18S6; Albatross; 1 young 

 female (16302). 



Dry Tortugas, Florida; W. 11. Longley; 1 imma- 

 ture female, holotype (50442). 



Caracas Bay, Curasao; in coral; April 2, 1920; C. 

 J. van der Horst; 1 young (Amsterdam Mus.). 



