THE SPIDER CRABS OF AMERICA 487 



West Indies; 1 female (Copenhagen Mus.). 



Near Colon, Panama; lat. 9° 32' 00" N.; long. 79° 54' 30" W.; 

 34 fathoms; brk. Sh.; April 2, 1884; station 2146, Albatross; 1 male 

 <7780). 



MACROCOELOMA CONCAVUM Miers 



Plate 170, fig. 3; plate 171, fig. 3 



Macrocoeloma concava Miers, Challenger Rept., Zool., vol. 17, 1886, pp. 79 

 and 81, pi. 10, figs. 2-26 (type-locality, Fernando Noronha, 7 to 20 fathoms; 

 type in British Mus.). 



Macrocoeloma concavum Rathbun, Proc. U. S. Nat. Mus., vol. 21, 1898, 

 p. 576; Bull. U. S. Fish Comm., vol. 20, for 1900, pt. 2 (1901), p. 75. 



Diagnosis. — Rostral horns triangular, separated by a V-shaped 

 sinus. A spine present on urogastric region. A transverse row of 

 five spines in line of cardiac spine. A strong protogastric spine. 



Description. — Body and legs covered with a short, close pubescence, 

 with some longer curled hairs. Carapace very convex, deeply 

 concave on hepatic regions; dorsal surface armed with ten spines, 

 disposed as follows: Three small spines in a triangle on gastric 

 region, of which the posterior, or mesogastric one is the largest; a 

 urogastric, a cardiac and an intestinal spine; a strong spine at lateral 

 angle of carapace, and in the same transverse line with this and the 

 cardiac spine, a dorsal, branchial spine. A few tubercles in front of the 

 mesogastric spine. Lateral margins of carapace tuberculated, the 

 tubercles continued in an oblique series over pterygostomian regions 

 nearly to antero-external angle of buccal cavity. Rostrum fiat, 

 intermediate in size between those of M. eutheca and M. inter- 

 medium; outer margins straight or concave; horns separated by a 

 V-shaped interspace as in intermedium. The orbits are less elongate 

 than in the two preceding species; besides a blunt preocular and 

 postocular tooth there are two or three tubercles on the upper margin, 

 and three teeth or lobes on the lower margin, the middle one of 

 which belongs to the basal antennal segment. This segment has also 

 two equal spines, one on the anterior and one on the outer margin 

 of the ventral face; behind the latter are a few tubercles. 



Merus of chelipeds armed with tubercles on the margins, four on 

 the upper margin being the largest; also two tubercles on outer 

 surface, one on lower surface; inner surface granulate. Carpus 

 granulate, a small tubercle at inner angle. Palm granulate on inner 

 surface, also a tubercle at proximal end. 



Measurements. — Female (24214), length of carapace measured 

 from posterior margin to tip of rostral horn 35.8, length measured 

 from between horns 32.8, greatest width at orbits 21.5, greatest 

 branchial width 33.2, branchial width without spines 28.6, width at 

 narrowest point behind orbits 18.1 mm. 



