REPORT ON THE AMPHIPODA. 309 



"Spec. 2. Gammarus I'errucosus, mh. n. sp. Corpore lateraliter compresso ; thorace et abdomine 

 inermibus, segmentis postabdoiuinalibus prKsertim, secnndo et tertio, tubercuKs numerosis 

 spinosis instructis ; ramo stylorum caudalium posticorum externo longissimo, margine longe 

 ciliato," found in the Angara at Ii-kiitsk, with Gammarus atchensis, Brandt, for its nearest 

 relation. This species is partially described and figured in the Brit. Mus. Catal., but there 

 by a misapprehension referred to "Brandt, Middendorff's Sibirische Reise." Spence Bate's 

 description of the pleon includes a feature not alluded to by Gerstfeldt in the " infero- 

 posterior angle of the third segment produced into a long upturned tooth." Dybowski, 

 however, in his account and figure of the species, does not give this tooth or anything more 

 than an ordinary angle to the segment in question. 



Spec. 3. " Gammarus Maackii, mh. n. sp. Corpore lateraliter compresso, thorace et anteabdomine 

 inermibus ; segmentis postabdominalibus singulis duabus vel quatuor carinis spinosis armatis ; 

 ramo stylorum caudalium posticorum externo longissimo, margine breviter aculeato." It 

 comes near to Gammarus oeliotensis, Brandt, and is almost as common in the Angara at 

 Irkutsk as Gammarus verrucosus. In the Brit. Mus. Catal., where it is figured, it is 

 attributed to Brandt, instead of Gerstfeldt. It is red escribed by Dybowski in 1874, but 

 not figured. 



As distinguished from the foregoing species, in which " Die Riickenseite des 4. und 5. Schwanz- 

 giirtels erscheint mit Stacheln besetzt," in the following species the fourth and fifth pleon- 

 segments are dorsally " stachellos." 



" Spec. 4. Gammarus eaneellus, Pallas," is described, with " tuberculorum (doKalium) par 

 quintum maximum." In 1862 Spence Bate took this as type of his new genus Pallasea. 

 In 1874 Dybowski again describes it as Gammarus eaneellus, Pallas, of which he describes 

 and figures a variety named GerstfeldtU." 



" Spec. 5. Gammarus cancdloides, mh. n. sp.," from the Angara at Ii'kutsk, is thus described : — 

 " Gammaro Cancello Pall, similis, tuberculis tamen dorsalibus minus elevatis ; a capite ad 

 caudam crescentibus, neque vero pari quinto, sed paribus octavo et nono maximis ; in seg- 

 mentis thoracis et anteabdominis carinarum lateralium loco tuberculis valde prominentibus." 

 Spence Bate, in the Appendix to the Brit. Mus. Catal., inclines to regard this as a variety 

 of Pallasea eaneellus, but Dybowski retains it as a distinct species, Gammarus eancelloides, 

 Gerstfeldt, of which he gives a description and figures. 



" Spec. 6. Gammarus latissimus, mh. n. sp.," also from the AngarA at Irkutsk is thus described : — 

 " Corpore latissimo, fere ouisciformi ; fronte producto et quatuor paribus aculeorum, mediis 

 duobus verrucis impositis, armato ; segmentis thoracis et anteabdominis carinatis et tubercula 

 supra laminas laterales sita versus declivibus; segmentis postabdominalibus tuberculis 

 lateralibus destitutis, anterioribus tribus tuberculis dorsalibus, quorum duo posteriora aculeata, 

 prseditis." As already explained, this species was subsequently under a misapprehension 

 attributed to Brandt in the Brit. Mus. Catal., and is there made the type of a new genus 

 Brandtia. Dybowski, who had not met with it in Lake Baikal, retains it under the name 

 Gammarus latissimus, in 1874. 



Among those Gammari in which "der Hinterrand des 3. Postabdominalsegmentes und meist 

 auch derjenige der beiden vorhergehenden verlangert sich in der MittelHnie in Art eines 

 Zahnes oder Stachels nach hinten," Gerstfeldt places "Spec. 7. Gamrnar)is kiirgensis mh. n. 

 sp. Corpore lateraliter compresso, margine posteriore trium anteriorum segmentorum 

 postabdominalium et interdum etiam nonnuUorum aut omnium anteabdominis et thoracis 

 in spinam acutam tenuemque segmento sequenti incumbentem producto," " aus einer Pfiitze 

 an der KUrga." This does not appear to be mentioned in the Brit. Mus. Catal. Nor does it 

 appear in Dybowski's long list of species from Lake Baikal. The fuller description is as 

 follows : — " Der Korper ist ziemlich stark seitlich zusammengedi'iickt ; die Stirn bildet nur 

 era kurzes dreieckiges Spitzchen ; die Augen sind oval-niereuformig. Die nur schwach 



