1908.] GENUS OF AMPHIPOD CRUSTACEA. 37S 



in immediate sequence to the Hyperina because of the agree- 

 ment which he considered to exist between that family and the 

 Hyperida; and Orchestida?. The Prostomatidfe are in close 

 relationship with the Lysianassid?e and might, in my view, well 

 be included in the older family." Stebbing was the first to per- 

 ceive the great resemblance between the Mediterranean and 

 Norwegian forms, and says (p. 272) of Guerinia nicceensis : " It is 

 beyond doubt, generically, perhaps also specifically, identical with 

 the later Trischizostoma raschii Esmark & Boeck, 1860"; and 

 again (p. 321) of Trischizostoma, " the genus, at least, is assuredly 

 a synonym of Guerinia Hope & Costa." 



In 1890, Sars (13) demonstrated clearly that Trischizostoma is 

 a true Lysianassid, basing his conclusion on the structure of the 

 oral parts, anterior antennte, posterior gnathopods, and the bi- 

 articulate 3rd uropod, and pointing out that "the urosome, which 

 Boeck considered Hyperiidean in character, essentially dififers by 

 being divided into three distinct segments." He, therefore, 

 places the genus in the family Lysianassidae, giving detailed 

 descriptions and figures of the adult female and the young form. 

 In the summers of 1890-91 Sars obtained several specimens, all 

 females, most of them ovigerous, in the Throndhjemsf jord, on the 

 common black dogfish {Sjyinax niger). The Lvi-gest measured 

 28 mm. 



Bonnier in his discussion of the " Lysianassides " (14) 1892, 

 refers to the difficulty of differentiating between the various 

 genera, and suggests " des diagnoses courtes basees sm- les 

 veritables diff"erences morphologiques de la structure des somites 

 et leurs appendices, ou des clefs dichotomiques permettant 

 d'arriver au genre et a I'espece par I'examen d'tui petit nombre de 

 caracteres, sans avoir a comparer une a une les descriptions et les 

 figures des nombreux types qui constituent la famille des Lysianas- 

 sides." He first gives the characters common to the family, and 

 then proceeds to characterise the dififerent genera according to the 

 strvicture of the 1st maxilla, the maxilliped, the 1st perseopod, 

 the telson and the antennule. The 1st maxilla in particular he 

 considers useful in characterising most of the forms ; for example, 

 the four genera, Trischizostoma, Acidostoma, Acontiostoma, and 

 Amaryllis are at once distinguished from the rest by the modifi- 

 cation of the maxillary palp. He discusses at length the con- 

 clusions of Bovallius(ll)and Sars (13), agreeing however entirely 

 with Sars. 



In 1893, Delia Valle (15) in his ' Sistematica ' gives 10 sub- 

 orders of the Gammarina, the tenth, Lysianassidse, including the- 

 two genera — Guerina and Trischizostoma. On p. 770 he points 

 out that the essential characters for distinguishing the Lysianassid 

 genera are — the peduncle of the anterior an fcennse ; the mandible ; 

 and the posterior gnathopod. In the table following, Giterina 

 and Trischizostoma (placed in close relation to Amaryllis and 

 Acidostoma) are defined thus: "Nei gnathopodi anteriori dell' 

 adulto I'articolazione del 3°, 4°, e 5°, articolo e tale che il margine 



