OXYSTOMATOUS AND ALLIED CRABS OF AMERICA 221 



reaching to tip of merus or nearly so. Chelipeds with a great spine 

 on merus (not carpus) placed in a horizontal plane and pointing out- 

 ward in a direction exactly transverse to axis of body. Ambulatory 

 legs with slender dactyli. 



From Massachusetts to the Windward Islands. 



KEY TO THE SPECIES OF THE GENUS ACANTHOCARPU8 



A.' Carapace narrowing in posterior half; a short spine on postero- 

 lateral margin alexandri (p. 221) 



A.* Carapace subcircular; a long spine on posterolateral margin. 



bispinosus (p. 224) 



ACANTHOCARPUS ALEXANDRI Stimpson 



Plate 69, Figures 1, 2 



Acanthocarpus alexandri Stimpson, Bull. Mus. Comp. Zool., vol. 2, p. 153, 1871 

 (type locality, off the Quicksands, Florida Keys, 74 fathoms; type not 

 extant). — A. Milne Edwards, Bull. Mus. Comp. Zool., vol. 8, p. 19, pi. 1, 

 fig. 2, 1880.— S. I. Smith, Proc. U. S. Nat. Mus., vol. 3, p. 418, 1881; BuU. 

 Mus. Comp. Zool., vol. 10, p. 7, 1882. — A. Milne Edwards and Bouvier, 

 Mem. Mus. Comp. Zool., vol. 27, p. 126, pi. 24, figs. 9-11; pi. 25, fig. 7, 1902.— 

 Schmitt, Carnegie Inst. Washington Year Book, no. 30 (1930-31), p. 393, 

 1931. 



Diagnosis. — Carapace ovate, with a short posterolateral spine. 

 Posterolateral margin not tuberculate. A tooth on posterior margin 

 and a conical tubercle on sternal plastron. 



Description. — Carapace regularly convex, widest in anterior half, 

 surface uneven, the protuberances arranged obscurely in five longi- 

 tudinal rows anteriorly, the middle ones of which form centrally and 

 posteriorly three conspicuous ridges, the lateral ridges terminating in 

 the spines of the posterolateral margin. Surface covered with minute 

 granules and punctae. Posterior margin arcuate, bearing a prominent 

 tooth at middle and a slight wave in the outline on either side. 

 Anterolateral margin with four slight tuberculiform teeth. Orbits 

 large, without fissures except the inner superior one which is nearly 

 obsolete; orbital margm ciliated. Front of moderate width, trilobed 

 in dorsal view, separated by a notch from the orbit. 



The spine at outer angle of merus may be a little longer or shorter 

 than half the width of carapace; the superior spine is one-fourth to 

 one-third as long as the inferior. Hand with a 7-toothed crest above 

 and another, oblique, 6-toothed crest on outer surface, extending from 

 base of dactylus to postero-inferior angle. On the latter crest the 

 posterior tooth is largest and forms by itself a short crest, separated 

 from the other teeth by a considerable interval. Between the upper 

 and lower crests of hand there are six or seven scattered tubercles. 



Stridulating ridge on inner surface composed of about 45 obUque 

 striae closely placed. Ambulatory legs naked, unarmed, with smooth 

 polished surface. A conicle tubercle on either side of first article of 

 sternal plastron. 



