160 CARL BOVALLIUS, AMPHIPODA HYPEEIIDEA. I. 2. HYPERIIDJE. 



Hyperia hystrix. 



Hyperia hystrix is an intermediate form between H. medusarum and //. galba, 

 easily to be distinguished from both: from the former by the short bristles on the first 

 two pairs of perseopoda, by the produced carpus of the first pair and by the short telson; 

 from the latter by the notched not serrated hind margin of the metacarpus of the first two 

 pairs and by the dense covering of short bristles on the same pair. 



The body is more elongated and compressed than in the preceding species; the 

 perason is shorter than the pleon and urns together. The surface of the segments is 

 smooth and even as if polished, flat or rather somewhat transversely concave. 



The head is somewhat shorter than the first two perseonal segments together, as 

 long as broad, and much deeper than broad. The antennal groove is large, commencing 

 a little above the middle of the front side of the head, and fully as high as broad. 



The eyes occupy almost the whole surface of the head. 



The first pair of antennas (PI. IX, fig. 23) in the adult male are a little longer 

 than the second pair, equal in length to the head and the first six pergonal segments 

 together. The first joint is thick, a little broader than long, and more than twice as 

 long as the two following joints together; the second joint is twice as long as the third. 

 The first joint of the flagellum is not quite twice as long as the whole peduncle, thick 

 at the base, with bulging sides, tapering towards the apex; the inner and under sides are 

 densely covered with long olfactory hairs; the two following joints are small, the fourth 

 longer, the fifth and sixth increasing in length, the seventh and following still longer, 

 equal in length, about eight times as long as broad. The flagellar joints are twenty-two 

 to twenty-four in number. 



The second pair of antennas (PI. IX, fig. 24). The first visible joint of the peduncle 

 is thick, nearly twice as long as the second, at the side of it projects the glandular 

 cone; the last peduncular joint is longer than the first, but shorter than the first and 

 second together. The first flagellar joint is somewhat shorter than the last joint of the 

 peduncle; the second and following joints are equal in length, about eight times as long- 

 as broad. The flagellar joints are about twenty in number. 



The labrum is protruding, longer than broad, deeply bilobed. 



The mandibles have a very thick and egg-shaped stem which at the outer margin, 

 below the middle, shows a broad tubercular projection, serving for the insertion of 

 the palp. The incisive lamina extends just below the molar tubercle, is narrow, and armed 

 with half a dozen sharp teeth. The first joint of the palp is short and thick, the second 

 is scarcely half as thick as the first and much longer, the third is still longer, fully twice 

 as long as the first, narrowly lanceolate, sharp-pointed, the outer margin densely fringed 

 with minute hairs. 



The first pair of maxillae. The apical portion of the principal lamina is smaller 

 than that part in the preceding species but more strongly armed with teeth and bristles. 

 The outer convex margin of the secondary lamina is densely set Avith teeth-like spines 

 and minute bristles. 



The second pair of maxillae. The projecting portion of the principal lamina is 

 conical, and covered with long slender bristles on its lower part; the secondary la- 



