n p DJ 



ISOPODA. 



AfUui mftflieut (Holta aquatita, Fabr.), female, magnified. 

 a, upper tide ; 6, under tide. 



and that it U very common on the English coast, under stones and 

 among the tea- weed. 



6. CLOFORTIDH (O*itcida, Latreille). This, the last section of 

 Itopoda, according to the arrangement of M. Latreille, consists of 

 thoM fonns which have indeed four antenna- , but the two intermediate 

 one* are very small, little apparent, and consist of two joints at most : 

 the lateral antenna- are setaceous. The tail is composed of six 

 segments, with either two or four needle-shaped appendages at the 

 posterior border of the last segment, and without lateral fins. Some 

 are aquatic, others terrestrial In the latter the first leaflets below 

 the tail exhibit a row of small holes, where the air penetrates to the 

 organs of respiration there inclosed. 



Home bare the sixth joint of their antennes, or their stem, so com- 

 posed that in counting the small articulations of this part the total 

 number of all the joints U nine at least. These are marine, and 

 consist of two sub-genera. 



Lima (Fahr.). Stem of the lateral antenna) composed of a great 

 number of small joints, and two very projecting stylets, separated at 

 the end into two branches, nt the posterior extremity of the body. 



Ijfla tertmiea, natural ilxe. 

 , upper aide ; 6, under ilde. 



L. otfamifa is very common on the sea-coast, where it may be seen 

 creeping on the rocks or on sea-walla. When an attempt is made 

 to seiM it, the animal quickly folds its feet and lets itself drop. 



Ty/o* (Latreille). Then seem to have the faculty of rolling them- 

 nelvr* np. The last segment of the body is demicircular, and exactly 

 fllls the notch formed by the preceding. The posterior appendages 

 re very small and entirely inferior. The antenna) have only nine 

 joints, the last four of which compose the stem. On each side is a 

 UibrrcU representing one of the intermediate antenna ; the inter- 

 mediate space is elevated. The branchiw are vesicular, imbricated, 

 and covered by laminso. 



T. A rmiulUlo, an inhabitant of the Mediterranean, may be taken as 

 aa example. 



/'kiloKia (Latrcill*). Lateral antenna; divided into eight joints and 

 xpneed at their base. The four posterior appendages nearly equal 

 T|MM occur in moist place*. Onucut lylrrttrii ( Kabr.) is an example. 



CUftrla, properly so called ; OKUCUM, Linn. (Wood-I.ice). Eight 

 jotoU to the lateral antennas, but their bate is covered ; and the two 

 external appendage* of the tail are much larger than the two internal 

 MB. Tb*M animal* frequent dark and retired place*, such as caves, 

 rUara, bole, in walla, ftc., and are also f.,<in.| ui,,l,. r stone* and old 

 log*. Their food ootMMUof decayed vegetable and animal substance* ; 

 and they scarcely evtr com* forth from their retreat* except in raiuv 



scarcely 

 or notsi weather. 



their retreat* except in rainy 

 They move slowly when not in danger. The eggs 



are inclosed in a pectoral pouch. The young at their birth have a 

 thoracic segment, short, and consequently only twelve feet These 

 Crtutacta were formerly used in medicine ; but they no longer form 

 part of the Materia Medica. 



Wood.Lonse (Onitcui mumritu). 



Porcellio (Latreille). Distinguished from the true Wood-Lice by 

 the number of joints of their lateral antenna;, which are only seven. 

 In other respects Porcellio resembles Onitcut. 



A rmadillo (Latreille). The posterior appendages of the body are 

 not projecting; the last segment is triangular. A small blade, in 

 form of a reversed triangle, or more large and truncated at the end, 

 formed by the last joint of the lateral appendages, fills up on each 

 side the void between the segment and the preceding. Lateral 

 antenna) with only seven joint*. The upper subcaudal scales am 

 pierced with a row of small holes. 



a 



Armadillo pmtulaliis. 

 a, expanded ; *, rolled up. 



Such is the arrangement of M. Latreille. 



Lamarck divided the liopoda into two great sections: the first 

 consisting of those which have the branchia) situated under the tail, 

 and comprising two subdivisions; the second composed of those 

 which have their branohia) placed under the anterior part of the 

 abdomen, between the feet. 



Under the first he arranged the genera Armadillo, Oniicus, Philotcia, 

 Ligia, AitUui, Idotea, Sphttroma, Cymotkoa, Bopyrut, Typhit, Ancevn, 

 Praniza, Apteudet, and Joru. Under the second he included the 

 genera Leptomtra, Caprella, and Cyamut. 



H. Desmarest also divided the liopoda into two great sections, 

 with many subdivisions. 



His first section, which he makes equivalent to the Phytibranchiato 

 Isopods of. Latreille, consists of the genera Typhit, Anceut, including 

 Unathia of Leach, Praniza, Eupheui, and lone. 



His second section, which he makes equivalent to the PWrygi- 

 branobes of Latreille, comprises the genera Idotea, Strnotoma, A nth ura, 

 Serotii, (Jampecopea, Ncua, Cilicaa, Cymodocta, Dynamene, Ztuara, 

 Sphavoma, *rydice, Neloeira, Cirolana, Voniltra, RocintUa, jfiga, 

 Canolira, AniUxra, Oltncira, Nerocila, Livontxa, Cymothoa, Limnoria, 

 Atelltu, Janira, Jcera, Ligia, Philotcia, Onucut, Porcellio, Armadillo, 

 and Bofiyrui. 



M. Milne-Edwards (edition of Lamarck, 1838) states, in a note to 

 that part of Lamarck's definition of an Isopod Crustacean, ' mandibules 

 sans palpes^' that Lamarck, I^atreille, and most authors are in error 

 when they assign this character to the liopoda, for in a great number 

 of these Crustaceans the mandibles are provided with a palpiform 

 stem, entirely resembling that which may be seen in the greater part 

 of the^mpAiporfo. 



He further remarks that the respiratory lamella; nituated under 

 the abdomen are hardly ever bronchia;, properly so called, but only 

 one of the branches of the false feet become membranous and vascular, 

 as in one of the appendages of the thoracic feet in the Amphipoda. 

 The female of font, he observes, exhibits an exception, for she carries 

 ramose bronchia; on each sid of the abdomen. 



M. Milne-Edwards, in his notes, further states that those Cruttacea 

 whose respiratory appendages are placed under the thorax (which 

 Lamarck calls abdomen) ought not to remain in the order of liopoda, 

 but belong to the Lamodipoda of M. Latreille. The egg-pouch he 

 describes as being formed of the flabelliform appendages, which have 

 become foliaoeous, and are raised against the sternum. 



