CHUSTACEA OF THE MEEaUI AEUHIPELAGO. 165 



resemble each other, and have on the lateral margins three or 

 four incisions, which cause them to appear four- or five-toothed. 

 In M. distinctus the first two antero -lateral teeth are almost equal 

 to one another, the first toolh (the external orbital angle) 

 being scarcely larger than the second ; in M. elegans, however, 

 the second tooth is distinctly larger than the first. In both 

 species the front is less prominent than the anterior margin 

 of the buccal cavity ; but the median lobe of the anterior margin 

 of the buccal cavity is more prominent in M. elegans. 



The infraorbital ridge is very finely crenulate in the male, 

 even more delicately than in M. distinctus, and, as in that 

 species, the ridge is continued backwards nearly opposite to 

 the second antero-lateral incision. In M. distinctus the 

 ridge is composed of 25-30 small lobules, of which the first 

 eight or ten, constituting the orbital portion, are longer than 

 broad, and transversely sulcate above. In M. elegans, on the 

 contrary, the ridge consists in the male of 50-60 minute rounded 

 teeth or granules, which gradually and regularly decrease in 

 size backwards ; in the female, the ridge, as usual, is not pro- 

 longed backwards behind the orbits, and consists of 35 teeth, which 

 are similar to those of the male. 



As regards the pterygostomian regions and the shape and 

 structure of the outer foot-ja-RS, both species completely agree 

 with one another, but the abdomen of the male is a little diff'er- 

 ent. In M. elegans the first (or terminal) joint is triangular, 

 rounded, and shorter than broad at the base ; the second joint 

 is longer than the first, and broader than long, the proportion of 

 the breadth of its posterior margin to its length being as 3| : 2. 

 The third joint is much shorter than the seiond. 



The chelipedes of the male of M. elegans are nearly the same 

 size as those of 3£. distinctus, and their arms project as far 

 beyond the lateral margins of the carapace. The anterior legs 

 are, however, more or less unequal, the right or the left being 

 the larger ; the arms are somewhat thickened in the middle, 

 and again narrowed at the distal extremity, that part of the 

 anterior margin of the upper surface which bears the musical 

 crest projecting a little more forward than in M. distinctus. 

 The hands of the adult male much resemble those of the latter 

 species, the palm being longer than broad (high) ; but they are 

 a little less slender, the proportion of the length of the palm (of 

 the larger hand) to its breadth (height) at the distal eud being 



