298 THE VOYAGE OF H.M.S. CHALLENGER. 



IL AmphitJioe elongata, Tav. iii, fig. 5 ; 12. Amphithoe micrura, Tav. iii, fig. 2, referred by 

 Spence Bate to Pherusa fuctcola, Leach.; in agreement OTth Costa's own suggestion; 13. 

 Amphithoe semicarhiafa, Tav. iii, fig. 3, identified by Heller with Oammurella hrevicaudata, 

 M.-Edw., Costa himself suggesting that it may be the female of his own Oammanis 

 punrtimmms, for which see below. 



The genus Elasmopus is thus defined : — 



" Antennss superiores hisetm; inferiores artimdo prima inermi. Pedes qnatuor anteriores pre- 

 hensiles, secundi primis ma/ores ; sexjMstici elati, laminares, aiiicido ultimo iantum tereti." 



By Spence Bate and J. V. Carus this is made a synonym of Podocerus, Leach, but Boeck points 

 out that the cleft telson, the laminar branches of the third uropods and the large side-plates 

 exclude that identification. The type species is Elasmopus rajjax, Tav. IV. fig. 5. 



Li the genus Gammanis, Fab., Costa mentions numerous species ; 1. Gammarus locusta, Fab.; 

 2. Gammarus marinus, Leach ; 3. Gammarus ■fluviatilis (to which he gives the confused 

 synonymy, " AstacMs fluviatilis, Roes. — Squilla pidex, Deg. — Gammarus Roeselii, Gerv. — 

 Gammarus fluviatilis, Edw.") ; 4. Gammarus plumicornis, Tav. IV. fig. 1 ; 5. " Gammarus 

 OKvii," M.-Edw.; 6. Gammarus index (with the synonymy. Cancer pidex ? Lin. — 

 Gamm.arus pulex. Fab. — Gammarus fluviatilis, Edw. An. Sc. nat. — Gammarus pulex, 

 Zenk., Edw. Suit. h. Buff.," and the remark "Trovasi neUe acque dolci, al pari del gamm. 

 fluviatilis"); 7. Gammarus unguiserratus, Tav. IV. fig. 2, accepted as a Gammarus hj Sp. 

 Bate and J. V. Carus, though the back " perfettamente liscio " does not agree with their 

 definition of the genus, while by the upper antenuEe much longer than the lower, the 

 side-plates not very deep, and the three pairs of uropods reaching equally far back, it 

 establishes a provisional claim to stand in the genus Mxra (Leach) Sp. Bate ; 8. Gammarus 

 longicaudatus, Tav. IV. fig. 6, abeady mentioned in Hope, Catal. p. 45, a species " trovato 

 nelle acque potabili fluenti della cittk," apparently identical with Niphargus aquilex, 

 Schi0dte ; 9. Gaminarus montanus, Tav. IV. figs. 7, 8, also from Hope's Catalogue, 

 " raccolto nel lago del Matese," and said to come very near the preceding species, but to 

 differ essentially in the tliird uropods " notabilmente pid corti, sorpassando di poco quelli 

 del quarto [aneUo] ; per modo che il primo articolo dell' appendice primaria k poco piii 

 lungo del peduncolo, ed il secondo e poco piu della metJi del primo," differences perhaps 

 not of the highest importance (see Bate and Westwood, i. pp. 315, 317); 10. Gammarus 

 oMusunguis, A. Cost. (n. sp.) Tav. III. fig. 8, referred by Heller to Gammarella hrevi- 

 caudata, M.-Edw., as the male form, and so accepted by Carus on the authority of Sp. 

 Bate, who however retains Gammarus ohfusunguis, Costa; Heller's identification being 

 indeed not a little doubtful from the great diflference between the second gnathopods 

 of Costa's form and those of Gammarella brevicaudata, ^ , as generally known; 11. 

 Gammarus scissimanus, Tav. III. fig. 7, named by Heller Meira scissimana, and clearly 

 the same as Amphithoe truncatipes, Spinola, from Italy, mentioned in White's Catalogue, 

 1847, and afterwards described as Mxra truncatipes by Sp. Bate, in 1862, Costa's specific 

 name scissimanus therefore taking precedence; 12. Gammarus punctimanus, Tav. III. fig. 6, 

 referred by Heller, no doubt correctly, to the male of Gammarella brevicaudata, M.-Edw., 

 the likeness to which is noticed by Costa himself; 13. Gammarus hispinosus, Tav. III. 

 fig. 9. The Brit. Mus. Catal., p. 224, gives Gammarus punciatus, Costa, seemingly by 

 mistake for Gammarus punctimanus, with the observation, " Costa says that it is nearly 

 allied to Gammarella brevicaiulata. It appears to me to be nearly allied to the genus 

 Melita." 



The genus Geradocus is thus defined : — 



" Antennx superiores bisetse ; inferiores processu trabeculiformi cuspidato, cum earum pedunculi 

 articulo primo articidato anteaque porrecto prxditss. Pedes quatuor anteriores prehensiles, 

 secundi multo majores; sex postici articulo primo tantum dilatato." The process of the 



