430 EEV. T. R. R. STEBBING ON AMPHIPODA FROM 



Baikal; 6. C. caspius (Pallas), 1771, from the Caspian Sea; 7. C. atchensis (Brandt), 

 1851, from Isle of Atcha and Unalaschka ; 8. C. subcarinatus (Bate), ].862, from 

 Bering Strait ; 9. C. fluviatUis (Bosel), 1755, from rivers and ponds of Europe. To 

 these may be added, though with some doubt, C. macrophthalmus (Stimpson), 1853, fi-om 

 Grand Manan ; and C. mucronatus (Say), 1818, from Florida. 



ACANTHOGAMMAEUS, n. g. 



Body with median, more or less dentate, carina, and also lateral or marginal carinse 

 more or less developed. Head with very short rostrum. Fiftli side-plates much 

 shallower than fourth. First antennae the longer ; accessory flagellum iisually much 

 developed, always with more than one joint. Third and foiu*th perteopods with second 

 joint narrowed below. Third uropods with rami subequal, not foliaceous. Telson deeply 

 cleft. 



The generic name alludes to the dentate caringe. 



The species included are the following six from Lake Baikal, all instituted under the 

 generic name Gammarus by Dybowsky in 1874: — Cabanisii, Zienkoioiezii, Godlewskii, 

 Hodoszkoioskii, armatus, and parasiticKS. 



EXPLANATION OF THE PLATES. 



n.s., natural size. 



a.s., iipper antenna ; a.i., lower antenna. 

 I.S., upper lip ; l.i., lower lip. 



m., mandible; mx. \, 2, first and second maxillie ; map., maxillipeds. 

 gn. ], 2, first and second gnatliopods. 

 prp. 1-5, first to the fifth peraeopods. 

 jilp. \, 2, 3, first, second, and third pleopods. 

 ur. 1, 2, 3, first, second, and third uropods. 

 T., telson. 



Plate 30. 



A. Talorcliestia Deshnyesii (Audouin). 



The central figure is a lateral view of a young male specimen. The two gnathopods and second and 

 fifth perseopods are shown separately, magnified to the same scale, with parts oi: each more highly 

 magnified. 



B. Talorchestia tridentata, n. sp. 



The first and second gnathopods, and second and third perseopods, are magnified to the same scale, the 

 inner surface of the hand of the second gnathopods being shown separately ; parts of the three 

 other limbs are more highly magnified. 



