REPORT ON THE AMPHIPODA. 883 



" Upper Lip elongate, apieally strongly insinuate. 



''Mandibles elongate, often strong, apieally produced, little or not at all dentate; 

 secondary plate also produced and narrow, molar tubercle little, often obsolete; palp 

 elongate, robust, three-jointed. 



" Lower Lip with the inner plate small, situated near the apex. 



" First Maxillx more or less elongate; the palp sometimes long, two-jointed, some- 

 times almost obsolete, one-jointed. 



" Maxillipeds with the inner plates long, narrow, furnished only with setse ; the 

 outer plates tolerably large or of moderate size and little setose; the palp not very 

 elongate, its last joint not unguiform ; the two last joints of the palp sometimes absent. 



"Body either compressed, thick, and furnished with large side-plates, or [sub- 

 depressed] not depressed, and furnished with smaller side-plates. 



" Upper Antennas without accessory flagellum. 



" First and Second Gnathopods sometimes slender and not subchelate, sometimes 

 robust and subchelate. 



" First and Second Perseopods strong. 



" The Fourth Perzeopods longer than the Third and the Fifth than the Fourth. 



" Uropods biramous. 



" Telson small, sometimes apieally incised." 



It is obvious that the words " non depressum" applied to the body, although 

 occurring in both of Boeck's works, are due only to an accidental error, and must be 

 corrected into " subdepressum," the word actually given in the account of Lafystius, the 

 only genus which can be in question. The description given of the Upper Lip, which 

 probably induced Boeck to transfer the Iphimedinge from the Gammaridse to the 

 Leucothoidae, is itself open to criticism, as inapplicable at any rate to some of the genera, 

 and it should, therefore, in my opinion, be removed from the definition. To include 

 the new genus Acanthechinus, I propose to make a slight change in the account of 

 the maxillipeds, describing the last joint as " not always unguiform," and in the account 

 of the mandibles to say that the molar tubercle is "generally little." 



Genus Acanthechinus, n. gen. 



General habit rigid, developing long pointed processes. 



Mandibles having a long palp, with a process on the first joint, the third joint not 

 shorter than the second ; the spines of the spine-row differing greatly in size and shape ; 

 the molar tubercle very prominent. 



First Maxillse with the inner plate small, carrying three plumose setae at the apex ; 

 the first joint of the palp not more than half the length of the second. 



