THE SPIDER CRABS OF AMERICA 473 



Measurements. — Male (46912), total length of carapace (to tips 

 of spines) 40, length from sinus between rostral horns to margin of 

 carapace 29.5, total width 36, width measured from anterior base of 

 postero-lateral spines 22.5 mm. 



Variations. — The rostral horns may be straight or slightly curved 

 (convex to each other); in length they range from one-sixth (15139) 

 to one-third (male, 46899) or more of the total length of the carapace. 

 The interspace varies from rather a narrow V (male, 46899) to almost 

 a right angle (46912). The postero-lateral spines may be straight 

 or curved (concave) upward (46901, 46884); and nearly transverse 

 (46912) or occasionally directed strongly backward (46887). 



Range.— '^ovth. Carolina; south and west Florida. 2 to 123^^ 

 fathoms. 



Material examined. — See table, pages 474-476. 



MACROCOELOMA HEPTACANTHUM (Bell) 



Plate 173, fig. 1; plate 269, figs. 8-11 



Pericera heptacantha Bell, Proc. Zool. Soc. London, vol. 3, 1835 (1836), 



p. 173 (type-locality, Puerto Portrero; type not extant); Trans. Zool. 



Soc. London, vol. 2, 1836, p. 61, pi. 12, figs. 6 (colored), 6r-6u (Puerto 



Portrero, Central America, on sand, 13 fathoms). 

 Macrocoeloma heptacantha Miers, Challenger Rept., Zool., vol. 17, 1886, 



pp. 79 and 81.— Rathbun, Proc. U. S. Nat. Mus., vol. 21, 1898, p. 576. 



Diagnosis. — Seven large spines on posterior half of carapace. 

 Front strongly deflexed; horns short. Basal antennal spine not 

 visible in dorsal view. 



Description. — Carapace suboblong, being proportionally wider just 

 behind the orbits and narrower across the postero-lateral angles than 

 in M. camptocerum. The seven spines of the hinder half are not very 

 unequal, and five of them form a nearly transverse line across the 

 carapace; they are the two pairs of branchial spines and the cardiac 

 spine. Of the three median spines the gastric and the cardiac are 

 erect, the intestinal spine is curved and directed upward and a little 

 backward. The inner branchial spine points upward, outward and 

 backward; the postero-lateral spine points slightly backward in a 

 horizontal plane. 



From the gastric spine the anterior half of the carapace including 

 the rostrum slopes steeply downward; horns short, acute and widely 

 divergent. This is the case in the specimens examined. In Bell's 

 figure of the adult the horns although widely separated are less oblique, 

 the interspace being more U-shaped. The orbits are turned outward 

 and a little forward ; the upper and lower margins are deeply incised, 

 the anterior and posterior teeth are acute. In Bell's figure^® 

 there is a good-sized marginal, hepatic spine; he does not mention 



«» Trans. Zool. Soc. London, vol. 2, 1836 ,pl. 12, fig. 6, 



