10 G. 0. Sårs. 



extend up the sides of the body to above the middle. The 

 strong mandibular palps issuing from the outer faces of 

 the mandibles extend obliquely forwards and downwards 

 between the bases of the inferior antennæ and the oral 

 aperture, their branchail appendage, however, being gener- 

 ally extended in the opposite direction. Behind the oral 

 aperture the anterior maxillæ are easily observed, with their 

 digitiform masticatory lobes, and the likewise digitiform palp 

 extending obliquely forwards towards the mouth. To the 

 outer side of these maxillæ is attached, the large semilunar 

 branchial plate extending obliquely upwards. Close behind 

 these maxillæ the posterior ones may be partly traced, 

 with their flabelliform reflexed palps. Then follow close 

 together the 2 pairs of legs, the anterior of which are 

 generally extended from the shell below, acting anteriorly, 

 whereas the posterior ones are constantly kept within the 

 cavity of the shell, and more or less bent up across the 

 abdominal part of the body. Between the legs and the 

 insertion of the caudal rami is a rather long interval, of which 

 the greater part is occupied by the genital lobes. The 

 caudal rami are very movably articulated to the end of the 

 abdominal part of the body, and from the articulation a 

 strong chitinous stripe is seen extending along each side 

 of that part, strengthening the articulation. When at rest, 

 the caudal rami are generally extended straight forwards, 

 being applied against the ventral face of the body. By 

 the aid, however, of a number of strong muscles running 

 along the dorsal side of the abdominal part of the body, 

 and joining their base posteriorly, they can be suddenly 

 moved downwards and backwards so as to extend in the 

 direction of the axis of the body, thereby serving as a most 

 effective propulsive apparatus. 



