1226 THE VOYAGE OF H.M.S. CHALLENGER. 



Tribe II. AMPHIPODA CAPRELLINA. 



Head in general with the boundaries marked, but otherwise coalesced with the first 

 segment of the perseon ; exceptions rare {Platycyamus). 



The second to the seventh segments of the Perseon as a rule distinct ; occasionally two 

 of them coalesced [Platycyamus thompsoni, Protella haswelliana)} 



Pleon degraded, consisting. of one, two, or (Cercops) five small segments. 



Eyes two. 



Antennae, two pairs ; the upper larger than the lower, without accessory flagellum. 



First Maxillae with the inner plate undeveloped. 



Maxillipeds with (Caprellidse) or without (Cyamidas) two 2 pairs of plates, and generally 

 with the palp four-jointed ; the palp rarely one-jointed (Platycyamus). 



The side-plates of the perseon never largely developed. 



Pleopods wanting ; lire-pods never more than two 3 pairs, and those more or less 

 rudimentary. 



In 1813 Leach established the Caprellini as sixteenth family of the Class Crustacea, 

 and fourth family within the tribe Gasteruri, giving for it the following brief definition — 

 " Body six-jointed, all the articulations except the second and third bearing feet. Two oars 

 on each side, placed on the sides of the second and third joint." As he assigned to this 

 family the two genera Caprella and Cyamus, it is practically equivalent to the Amphipoda 

 Caprellina. In 1814 Leach changed the name Caprellini into Caprellides, which he called 

 the fourth tribe of Gasteruri, including in it the new genus Proto. In 1815 and 1816 

 he took what must be considered a backward step, since in the third section of the 

 legion Edriophthalma he united this group with the Isopoda. He made it the first 

 division of its section, improving the classification by forming two subdivisions, the first 

 for Proto and Caprella, the second for Larunda [Cyamus], but erroneously assigning 

 "Pedes 14" as a general character of the division. 4 See Notes on Leach, 1813 (p. 84), 

 1814 (p. 86), 1815 (p. 90). In 1817 Latreille established the order Lasmodipoda to 

 receive this group, which he had previously, under the name Cystibranchia, combined 

 with the Isopods. See Notes on Latreille, 1817 (pp. 95, 99). For further definitions 



1 In Platycyamus thompsoni (Gosse) Lutken says that the branchiferous segments, that is, the third and fourth, in the 

 female though not in the male, are coalesced for the greater part of their breadth ; in Protella haswelliana, Mayer says 

 that the sixth and seventh segments are coalesced. 



2 In Cercops Kr0yer observed only one pair of plates, but thought that the second pair had by its small size escaped 

 his observation. 



3 The " two very small, oval or vesicular organs " at the base of the first uropods in Cercops, which Kr0yer figures and 

 describes, cannot, with respect to their form and position, be regarded with any probability as representing either pleopods 

 or uropods. 



4 In the Encyclopaedia Britannica, Art. Annulosa, p. 423, he says without qualification, " Division I. Body with all 

 the segments bearing legs." In the Trans. Linn. Soc. Lond., vol. xi., he says of the legs, "paria tertium et qnartum 

 saepius spuria," no doubt in allusion not to rudiments of the actual legs but to the branchiae. 



