CRUSTACEA. 659 



Add genera : Cerapus SAY, A tylus LEACH, Podocerus LEACH, &c. 

 Comp. MILNE EDWARDS, Hist. Nat. des Crust, in. pp. 58 70. 

 Genus Erichthonius MILNE EDWARDS, on the authority of KROEYER, 

 does not differ from Podocerus, but rests on a sexual difference of 

 the males. TidssJcr. iv. 1842, pp. 163, 164. 



B. Four first segments of trunk with epimera large, covering 

 the bases of feet. Abdominal feet six; the last terminated by 

 styles, serving with the apex of the incurved tail for jumping. 



Body depressed. Anterior either all or the inferior terminated 

 a filament setaceous, multiarticulate. 



Talitrus LATE. Mandibles furnished with a rudiment only of 

 )alp or destitute of palp. Superior antennae not longer than head, 

 horter than the pedicle of inferior; inferior elongate* 



Genera : Talitrus and Orchestia LEACH. 



Sp. Talitrus saltator EDW., Cancer locusta L., PALL. Spic. Zool. IX. Tab. 4, 

 fig. 7, DESMAR. Crust. PI. 45, fig. 2, Cuv. R. Ani. ed. ill, Crust. PI. 59, 

 fig. 3. This little animal, about " in size, is very common on the Dutch 

 coast, where it is constantly progressing in the sand by jumping. 



Orchestia is distinguished by the sheer-shaped form of the first and 

 second pairs of feet; the second pair has a large oval joint at the apex, on 

 which the moveable curved claw is set; here belongs Orchestia littorea 

 LEACH, EASIER Natuurk. Uitsp. ii. Tab. 3, figs. 7, 8, DESMAR. Crust. 

 PI. 45, fig. 3- 



Gammarus LATR. (Species from genus Gammarus FABR.). 



Mandibles furnished with palp. Superior antennae always longer 



ihan the peduncle of inferior, sometimes longer than inferior 

 hemselves. 



Sub-genera : Lysianassa EDW. (Anonyx KROEYER), Alibrotus 

 EDW. (Lysianassa previously), Phlias GUERIN, Acanthonotus OWEN, 

 Iscea EDW., Anisopus TEMPLET., Amphitoe LEACH, Gammarus EDW., 

 Ischyrocerus KROEYER, Leucothoe LEACH (Lycesta SAV.) and some 

 others proposed by KROEYER 1. 1. 



Sp. Gammarus fluviatilis EDW., Gammarus pulex KOCH, RCESEL Ins. in. 

 Suppl. Tab. 62 ; KOCH and GERVAIS distinguish this species as Gammarus 

 Rceselii from Gammarus pulex FABR., DESMAR. Crust. PL 45, fig. 8, Gam- 

 marus fossarum KOCH in HERRICH-SCH^SFFER Deutschl. Ins. Heft 138, 

 Tab. i. LINNAEUS has confounded not only these two species, but also 



422 



