CETJSTACEA OF THE MEEGTJI AECHIPELA&O. 127 



culate, presenting four or five minute teeth. The third tooth is 

 very small, and separated from the preceding by a minute notch. 



The structure of the inferior orbital margin of the male is 

 very characteristic, and difierent from that of M. quadratus. 

 The inferior orbital margin presents in its middle a broad, 

 though little prominent, slightly triangular lobe, which is 

 directed somewhat downwards, its obtuse tip being found 

 at the internal or median side ; the upper surface of this lobe 

 is slightly concave. Behind this lobe, the inferior margin of 

 the orbits presents a second, also obtuse, much smaller lobule, 

 which is found at the external end of the under margin ; whereas 

 the internal or median part of the under margin, lying 

 between the larger middle lobe and the epistome, is armed with 

 a row of seven or eight minute rounded granules, the external 

 one of wh-ich is the largest, whereas the others successively 

 decrease in size towards the epistome, i. e. towards the inner end 

 of the orbital margin. 



The inferior orbital margin of the male M. quadratus, on the 

 contrary, presents three prominent rounded lobes. In the 

 female the inferior orbital margin is regularly and delicately 

 crenulate, as in the female of M. quadratus. The eye- 

 peduncles are quite as long as the orbits. The somewhat 

 hairy pterygostomian regions and the inflected sides of the 

 cephalothorax present the ordinary structure seen in other species 

 of this genus. The external foot-jaws have also the ordinary 

 form. The sternum and the male abdomen are smooth and gla- 

 brous, and sparsely and minutely punctate ; all the joints of the 

 male abdomen are distinct. The abdomen of the female occupies 

 the under surface of the cephalothorax, lying between the legs, 

 and its margins are fringed with hairs. 



The anterior legs of the male are equal to one another in three 

 specimens and unequal in the fourth ; in their general appearance 

 they resemble those of M. quadratus. The anterior margin of 

 the arm, which is a little dilated at the distal end, and the two 

 other margins, are armed along their whole length with 

 many small acute teeth. The "musical crest" lies on the some- 

 what hairy, upper surface close to the middle of the anterior 

 margin and parallel to it. The outer and the under surfaces 

 are also hairy. The wrist presents some acute granules at its 

 internal angle ; its upper surface is smooth. The hands are 



