CBUSTACEA OP THE MEEGUI AECHIPELAGO. 157 



abnormal individual. In tlie male the chelipedes gradually appear 

 more elongate, according to tlie greater age of tlie individuals : 

 e. g., in a small specimen, the cephalothorax of which is only 

 20 millim. broad, the chelipedes, being 30 millim. long, are one 

 and a half times as long as the breadth of the carapace ; the 

 chelipedes of this specimen only project for a short distance 

 beyond the lateral margins of the cephalothorax, the arms 

 scarcely reaching to the distal end of the first third of the 

 meropodites of the third pair of legs. In the largest specimen, 

 on the contrary, the chelipedes are nearly two and a half times 

 as long as the breadth of the cephalothorax, and they are very 

 elongate, the arms reaching nearly to the distal end of the mero- 

 podites of the third pair of legs. The arms are triquetrous in the 

 male, presenting an upper, an anterior, and a posterior surface ; 

 they are somewhat thickened near the proximal extremity, and 

 also, although not so much, at the distal end. The "musical crest " 

 is situated near to the proximal extremity of the anterior margin 

 of the upper surface of the arm, and on the margin itself, so that 

 it lies exactly opposite to the infraorbital ridge, against which 

 it is moved and rubbed by the animal. In the female there is 

 no trace of the musical crest. 



As already stated, the chelipedes are comparatively much 

 shorter in young male specimens than in the adult. In a 

 young individual, the cephalothorax of which is 20 millim. 

 broad, the musical crest is placed on the middle of the anterior 

 margin of the arm ; so that at a still younger age it is probable 

 that the crest is situated near the distal extremity of the arm (as 

 in Helice), and that it gradually proceeds towards the proximal 

 extremity, in consequence of the growth of that part of the arm 

 lying between the crest and the distal extremity, the proximal 

 part not increasing in length. In the same specimen the hands 

 are less elongate than in the adult, and the fingers are a little 

 longer than the palm, whereas the immobile finger is scarcely 

 curved downward. 



The female specimen, carrying eggs, is scarcely more than 

 20 millim. broad. Its chelipedes are equal, project but little 

 beyond the lateral margins of the carapace, and are even smaller 

 than those of the male specimen of equal size. The fingers 

 are nearly once and a half as long as the palm. 



