REPORT ON THE AMPHIPODA. 1183 



it as the sixth family of the Amphipoda :— " Pedum caudalium unum vel pluria ahsunt 

 — Aberrantia, S. Bate," this character embracing also the families Caprellidae and 

 Cyamidge, the next being peculiar to the Dulichidae, " Cauda minime obsoleta, segmentis 

 6 composita." The telson is included as one of the six segments mentioned. Boeck in 

 1870 added two new genera, Paradulichia and Xenodice, and gave the following 

 definition of the family : — 



" Upper Lip very broad, apically subsinuate. 



" Mandibles strong, apically dentate, with the secondary plate large and dentate ; 

 molar tubercle robust ; spines of the spine-row few but strong, serrate at the extremity of 

 the convex margin ; the palp long, very slender, its third joint shorter than the second. 



" Lower Lip strong ; with the inner plates very strong. 



" First Maxillte with the inner plate larger or smaller ; the second joint of the palp 

 elongate, apically spined. 



" Maxillipeds having the outer plate armed with thick spines on the inner margin ; 

 the fourth joint of the palp thick, apically armed with one strong unguiform spine. 



"The body elongate, linear, depressed; the side-plates very small; the pleon 

 consisting of only five segments and furnished with five pairs of appendages, (the sixth 

 segment of the perseon generally coalesced with the seventh). 



" Upper and Lower Antennae subpediform, elongate, (the upper generally furnished 

 with an accessory flagellum)." 



The two statements which I have enclosed in brackets were added in 1876. In 

 1882 Sars places the Dulichiidse as the twenty-second and last family of the Gammarina, 

 with the four genera included in it by Boeck. The later definitions of the family by 

 Carus and Gerstaecker are quoted in the remarks on the genus Platophium. All writers 

 who have defined the family have not unnaturally laid stress on the want of the full 

 number of the segments in the pleon. Spence Bate considers that the sixth segment 

 is wanting. Haswell, in describing " Cyrtophium (?) hystrix," which he afterwards 

 transferred to Lsetmatophilus, speaks of "the absence of the fourth segment of the 

 pleon." Gerstaecker regards the fourth and fifth segments of the pleon as coalesced. 

 Of the three opinions this seems the most probable, but the further alternative, that 

 the fifth segment is wanting, may have better claims to acceptance than any of them. 

 However that may be, it is not so much the position of the missing segment, as the fact 

 of its absence or indistinguishable coalescence, that causes a very great difficulty as 

 regards classification. In the genus Platophium, as will be seen, the number of 

 segments is complete, and yet in other respects this genus bears so close a relationship 

 to Lsetmatophilus, that it cannot be satisfactory to classify them in different families. 

 In speaking therefore of the Dulichiidse as having only five segments and five pairs of 

 appendages to the pleon, the convenient expression plerumque, for the most part, ought 

 to be added. 



