CRtJSTACEA OF THE MEEGUI ARCHIPELAGO. 159 



still smaller than the third. The lateral margins are fringed 

 with short hairs, and the branchial regions of the upper sur- 

 face are marked with three minutely granular lines, the anterior 

 one of which is almost transverse, and terminates at the third 

 antero -lateral tooth, whereas the other two proceed obliquely 

 on the postero-lateral regions of the cephalothorax ; the latter 

 are slightly pubescent. The upper surface of the carapace is 

 a little convex, and the front is declivous and longitudinally 

 grooved in the middle. The anterior margin of the front, which 

 presents a small triangular incision in the middle, the breadth 

 of which measures somewhat more than a fourth of the distance 

 between the external orbital angles, makes very obtuse angles 

 with the lateral margins of the front. 



The front is a little less prominent than the epistome, so 

 that the latter is visible when the carapace is viewed from 

 above. 



The infraorbital ridge was described by Milne-Edwards as 

 " finement crenele ; " but these words are only exact when M. 

 distincfus is compared with M. indicus. In M. indicus, M.-Edw. 

 the infraorbital ridge is prolonged backwards to the level of 

 the^rs^ antero-lateral incision, and only presents nine or ten 

 teeth or lobules of very unequal size. The first four or five 

 teeth are very small, and slightly increase in size ; they are 

 followed by two large rounded lobules. Behind the latter, and 

 separated from them by a larger interval, three smaller, rounded, 

 postorbital tubercles occur, constituting the postorbital portion 

 of the ridge, and gradually decrease in size backwards. 



In Metaplax distinctus, on the contrary, the infraorbital ridge 

 is continued backwards, behind the orbits, to the level of 

 the second incision of the lateral margins of the carapace. In 

 this species the ridge is composed of 25-30 small lobules 

 which successively, though slowly, decrease in size backwards. 

 The first eight or ten lobules, which constitute the orbital 

 portion of the ridge, are longer than broad, the following as long 

 as byoad, and the posterior fourteen or fifteen much smaller 

 postorbital lobules are even a little broader than long. These 

 small lobules are distinctly transversely sulcate on their upper 

 margin. 



As in all species of Metaplax, the outer foot-jaws are widely 

 gaping and provided with an oblique piliferous ridge; the 

 merus-joint is nearly quadrate, being about as long as broad 



