Fauna Sulterranea. 151 



of abdominal legs, our animal belongs, as observed already by 

 Erichson, to the middle group (the family of Oniscida?, Koch), 

 characterized by the oval or lanceolate form of those legs, and 

 otherwise corresponding entirely with the almost identical divi- 

 sion of Porcellionides of M. Milne-Edwards. Among the genera 

 founded in this group by Latreille and Brandt, which differ only 

 in the number of joints of the outer flagellum of the antennae 

 (one, two or three), Pherusa maintains its place in many respects. 

 Instead of one single, or only a few joints, which in point of form 

 or size do not contrast with the outer joint of the stalk, we find 

 here a very developed flagellum, having a larger number of short 

 joints (eight, to twenty). The entire form of the animal is slender, 

 the corners of the hindermost of the thoracic segments are consider- 

 ably elongated, especially in the male, without the abdomen being 

 enclosed by the seventh thoracic segment, as is usually the case ; 

 on the contrary, it is quite free, more than half the length of the 

 thorax, receiving a still more determined shape, from the unusual 

 length of the two first joints ; these, as well as the succeeding 

 joints, differ in shape among themselves, as well as from the 

 thoracic joints ; the posterior corners of the third of the abdo- 

 minal segments, in the male, being much elongated externally and 

 backwards. The structure of the limbs is in uniformity with the 

 slender form of the body, the first seven pairs of legs being very 

 delicate, and increasing gradually in length from before, so that 

 the last pair is very much longer than the first, which is the re- 

 verse of what is the case in the known genera. The outer joints 

 of the last pair of abdominal legs is subulate, and exceeds in 

 length the abdomen. 



The following points remain to be noticed, being different from 

 the other genera of the group. The middle of the three lobes, 

 which seem to terminate the head anteriorly in these genera, may 

 be said to be deficient here, inasmuch as it does not, as usual, 

 form a projecting border, but is vaulted downwards with a gentle 

 curve towards the clypeus, above which it is bordered by a strongly 

 arched, slightly elevated line. All the parts of the mouth are re- 

 markably slender. In the sinus of the masticatory side of the 

 mandibulae are found four movable appendages ; the first of these 

 is thick, with a naked, toothed joint ; the other three elongated, 

 nearly filiform, slightly hairy on the anterior surface. The first pair 

 of maxillae have the anterior lobe at its apex furnished with three 

 appendages, instead of a short one ; they are long and slender, 

 nearly lanceolate, and furnished with longish lateral hairs. The 

 palpi and lobes of the maxillary feet are unusually developed, and 



