458 BULLETIN OF THE BUREAU OF FISHERIES. 



Chelipeds strong; meros with two strong spines or tubercles in front, five much smaller ones along 

 posterior margin and usually two on the upper surface near the posterior margin; carpus entirely 

 smooth or with a small spine near iimer distal angle; hand smooth, polished, and somewhat tumid; 

 fingers stout, widely gaping at the base but with expanded, hollowed-out tips; movable finger with 

 a single large tooth at basal third or with two or three small teeth; immovable finger with from one 

 to three teeth at the middle. Ambulatory legs spiny or denticulate and with many fine hairs. 



Dimensions of a male: Length of carapace, 13 mm.; width, 16 mm. 



Color, red, approaching vermilion and with little or no trace of purple. 



This species, which was formerly thought to be the common Mitkrax of the Beaufort region, is 

 unquestionably much less abimdant than the next, M. depressus. The two species, so far as can be 

 determined, live together imder the same conditions on the Blackfish Banks. Neither has ever been 

 taken within the harbor or close to the shore. 



Mithraz depressus A. Milne-Edwards. PI. xxxviri, fig. 2. 



Mithrax depressus A. Milne-Edwards, 1S73-1S80 [1875]. p. 96: Rathbun, 1901, p. 68; Verrill, 190S. p. 407. 



Carapace little if any wider than long, conspicuously tuberculate; spines of anterolateral border 

 well developed, the anterior one or two inclined to be double, while the posterior one or two are acute 

 and curved forward; on the gastric region there are five small tubercles in a transverse row and in front 

 of these two pairs of tubercles, the anterior pair being at the base of the rostral horns; on the mesogastric 

 region there are two tubercles on each side in a transverse line; on the cardiac region a group of three 

 or four poorly defined ones and on the branchial area four rather strong tubercles and several smaller 

 ones arranged more or less in three oblique rows which start at the anterolateral margin; front broadly 

 notched; lower anteorbital tooth considerably exceeding the upper one, its tip acute and strongly 

 incurved ; postorbital teeth much smaller than the anteorbitals. 



Chelipeds rather slender; meros with one blunt spine in front, five smaller ones on posterior margin 

 and a few on upper surface; carpus with several small tubercles; hand rather slender, upper and lower 

 borders nearly straight; fingers slightly gaping, dentate for nearly their entire length. Ambulatory 

 legs dentate and hairy. 



Dimensions of a male : Length of carapace, 15 mm.; width, 15.6 mm. 



Color, brownish red. 



It appears to be the commonest and most characteristic crab of the offshore banks, where it is 

 found in company with M. forceps. 



Mithras pleuracanthus Stimpson. PI. xxxvni, fig. 3. 



Mithrax pleuracanthus Stimpson, 1871, p. 116: Rathbun, 1901, p. 68. 

 Mithrax hispidus Rathbun, 1892 (pt.), p. 265. 



Similar in all general characters to M. depressus but with the carapace broader in proportion to 

 its length and with the anterolateral margins less arcuate. The rostral horns are shorter and wider 

 and placed closer together, the interspace tending toward a narrow V-shape. The tubercles of the 

 carapace differ in that the two of each pair on the mesogastric region are confluent. There are also 

 small tubercles about the base of each lateral spine. 



The two species are so much alike that, after they have been for a time in alcohol, only the closest 

 study and the comparison with well authenticated specimens of both species will make their separation 

 possible. It is probable , however, that living specimens of M. pleuracanthus may be readily recognized 

 by their color, which, judging from comparatively fresh specimens in formalin, is a much deeper red 

 with distinct crimson cast. 



Three or four specimens were taken on the Blackfish Banks in 1913 and 1914. 



Genus MICROPHRYS H. Milne-Edwards. 



Microphrys H. Milne-Edwards. 1851, p. 251. 



KEY TO THE SPECIES OP THE BEAUFORT REGION. 



a. Carapace without lateral laminiform processes; one branchial spine bicornutus. 



aa. Carapace with two lateral laminiform processes; two branchial spines platysoma. 



