2180 CRUSTACEA. 



His Peltidiurn* closely resembles Sapphirina in habit and external 

 form, and may be of that genus. The spectacle-eyes, or conspicilla, 

 are not represented ; but it was true also of the original description 

 of Sapphirina, that they were overlooked. 



Hersilia-f is in all probability related to the Caligidge, as Milne 

 Edwards observes; and as the specimen was but one and a half lines 

 long, it may have been young. 



Thyone% is very peculiar in its appearance, differing much from the 

 known genera of both the Cyclopoidea and Caligoidea. The outline 

 on Plate 71, fig. 115, from Philippi, gives its general form. The body 

 consists of but five segments, and the caudal stylets fill up a space in 

 the extremity of the body, as in some Spheromidae, instead of project- 

 ing beyond. The natatory legs have the usual Cyclops form, and are 

 but six in number. The first pair of legs, or the pair anterior to the 

 natatories, end in two small lamellae, somewhat like those of Psam- 

 mathe.§ 



Subfamily I. CYCLOPIN^]. 

 Genus CYCLOPS. 



As in the preceding family, we number the caudal setse 1, 2, 3, 4, 

 5, beginning with the inner one of each side. The first is shorter 

 than the third, and the fourth is shorter than the first ; the second is 

 the longest ; the fifth is quite short, and is situated on the outer side 

 of the stylet. 



The species of Cyclops swim freely, and with a saltating motion. 



* Philippi, Archiv fur Naturgeschichte, iv. 1839. f IWd -J P- 128t 



% Philippi, Archiv fur Naturgeschichte, iv. 1839. His description is as follows :— ^ 

 " Corpus depressum, scutiforme, ovatum, segmentis 5 constans, segmento lmo inaxi- 

 mo. Cauda e lamellis duabus formata. Oculi duo confluentes. Antennas 4; ante- 

 riores rnultiarticulatse ; inferiores 3-articulatse, apice setis uncinatis, basi seta pectinata 

 munitse. Pes masticatorius [nobis pes lmi] apice lamellis duabus laminatus. Pedes 

 sex natatorii birami. Pedes spurii duo, lamellares, spatium inter segmentum penulti- 

 mum caudamque opplentes." — Sp. Th. viridis, f '" long. 



§ The new species of Cyclopidae beyond, are briefly described in the Proceedings of 

 the Amer. Acad. Sci., i. 1847. 



