THE ISOPOD ailfUS OTJEOZEUKTES. 331 



I. The Cephalic Begion. 



The head is small and siibtriangular ia shape, sunk in a deep 

 notch between the lateral portions of the first thoracic segment, 

 whicli extend far forward on each side so that their anterior 

 borders are on a level with the eyes and almost reach the antennae. 

 The eyes are of moderate size, situated near the lateral margin 

 of the head, and densely pigmented. They are, of course, com- 

 pound, and the hexagonal lens-areas, as in other Cymothoidse, 

 are comparatively few in number and large in size. 



Below the anterior border projects very slightly a membranous 

 upper lip or labrum. 



Appendages of the Cephalic Region. 



(1) The first antennce are about 5 mm. in length, subulate, 

 pointed, and composed of seven joints. They arise below the 

 margin of the head-shield and are directed outward transverse 

 to the axis of the body. 



(2) The second antennce are in general similar but slightly 

 longer and more slender, and composed of eight joints. Their 

 origin is immediately behind that of the first pair, and the bases 

 of both are crossed at right angles by the mandibular palp. 



(3) The mandibles are of somewhat unusual form. They have 

 a strong conical base attached to the sternal region of the 

 segment some distance back, and rather far from the middle line. 

 Prom the distal end of this basal portion a much slenderer 

 calcified rod runs obliquely forward and inward, ending in a 

 transverse oval structure with a minute chitinous tooth meeting 

 its fellow of the opposite side. From the anterior outer angle 

 of the basal portion rises the soft, pointed, 3-jointed^a7p, which 

 is directed straight forward and, as already stated, crosses at 

 right angles the bases of the antennae (PI. XIV. figs. 3 & 5). 



Immediately behind the terminal plates of the mandibles comes 

 the soft bi-lobed labium, and the two together give a cruciate 

 appearance when the head is looked at from the front with 

 all the mouth-parts in place. The undersides of the labial 

 lobes are grooved for the reception of the succeeding pair of 

 appendages. 



(4) The first maxillce are reduced to a pair of cylindrical, 

 pointed, scarcely calcified styles which arise immediately to the 



