ANCEUS MAXILLAR1S. 189 



the antero-lateral angles thus formed : within the place 

 of insertion of the antennae on each side, the anterior 

 margin of the head is somewhat porrected, and trans- 

 verse, with a prominent tubercle on each side, the space 

 between these two tubercles being emarginate, with a 

 small prominence in the middle. The dorsal surface, of 

 the anterior half of the head, is depressed, an evident 

 channel running from the middle of the fore margin 

 to the centre of the head, where it meets with a small 

 posterior longitudinal caTina, behind which is a very short 

 transverse ridge (which may indicate the point of union 

 of the two segments of the pereion soldered to the head). 

 On either side, arising from the inner margin of the eyes, 

 is a short slightly impressed fossa, the surface of which is 

 more or less strongly granulated. The superior antennae 

 are about the length of the mandibles, slender, with two 

 equal-sized basal joints, a longer third joint and a five- 

 jointed flagellum reaching to the tip of the fourth joint 

 of the lower antennae, which latter are nearly as long as 

 the head and rather thicker than the upper pair, with two 

 short basal joints ; a third and fourth joint, more robust 

 and of nearly equal length (equalling that of the third 

 joint of the upper pair), and a short flagellum of six 

 articuli. The mandibles are of large size, being about 

 two-thirds of the length of the head. They are nearly 

 flat above, of a somewhat elongate- triangular form, with a 

 prominent tooth in the middle of the outer edge, the apex 

 prolonged into a curved tooth, and the inner margin armed 

 with nine or ten small obtuse teeth; the inferior sur- 

 face of the head is protected by a pair of large flat valve- 

 like organs, each about half the size of the head itself 

 (and which might be supposed to represent the second pair 

 of gnathopoda (z), corresponding with the second pair of 

 feet of the typical Isopods, but lettered g in the figures in 



