CETJSTACEA OF THE MEBGT7I AECHIPELAGO. 123 



the shape of its carapace, whicli is remarkably narrowed ante- 

 riorly. Nearly the whole upper surface of the cephalothorax is 

 covered with minute granules, but the mesogastric lobe is smooth 

 and frequently the middle of the anterior cardiac region. The 

 branchial regions present two somewhat oblique and parallel 

 granular ridges, and the margins also of the cephalothorax appear 

 granular. The lateral margins diverge considerably backwards in 

 this species, and present three incisions, the anterior being the 

 most distinct ; the second is found nearly in the middle, or 

 a little before the middle, of the lateral margin, and the third 

 incision is so very indistinct, that it may easily be overlooked. 

 A short transverse granular ridge is also found above the in- 

 sertion of each of the two posterior legs, close and parallel to 

 the posterior margin of the carapace. 



The chelipedes of the adult specimens are nearly equal to one 

 another. The upper margin of the arm is somewhat granular, 

 also the external margin; both the upper and the anterior 

 margins of the arm are clothed with rather long hairs. The 

 inner surface of the arm is armed with a short, horny, longi- 

 tudinal crest, situated close to and a little beyond the middle of 

 the anterior margin and parallel to it. This crest, which was 

 not described by Messrs. Eydoux and Souleyet, is doubtless 

 homologous with the " musical crest " of the genera Metaplax 

 and Selice, described further on. The chelipedes of the female, 

 as is usual, are much smaller than those of the male, and the 

 inner surface of the arm is not provided with the horny musical 

 crest characteristic of the latter sex. 



In the male, the upper surface of the wrist and the outer 

 surfaces of the hands and fingers are quite smooth ; the upper 

 margin of the palm, however, is a little granular at its proxi- 

 mal end. Both fingers have somewhat excavated, spoon- 

 like tips ; the inner margin of the immobile finger is armed with 

 a strong, minutely denticulated tooth a little before its middle, 

 and with a dozen very small teeth between the large tooth and 

 the tip. The mobile f ^ger is minutely granular on its upper 

 margin, when examined under a lens ; and its inner margin 

 presents a small, somewhat quadrangular tooth at the base, and 

 fourteen or fifteen very small teeth between the quadrangular 

 tooth and the tip, similar to those of the index. The inner 

 surface of the palm is unarmed, smooth, and covered with a close 

 down of hairs ; in many specimens, however, and perhaps always 



