D90PODA, 



ISOPODA. 



w <Utr*iUe; .\mcila, Lintuta, Leech).- Antenna of 

 equal Ictijth, MM! eyes not very visible ; lot segment of the body 

 n~rly triangular, with two pieces terminating the Utenl fin*, in 

 t-nii of loaflvU or blade* : Uie exUriorof these U greatest ill A'froc.Vo, 

 and of UM MOM ne as the othen in lironrro. 



M. Latrrille observes Out in the four following nib-genera the 

 tapenot antenna are manifestly shorter than the inferior. 



Wanv, as well H UM CymOetr, hare all the feet terminated by a 

 powerful and strongly-arched nail (onglet) ; the lat eight are not 

 piny ; the eyes are always distant and convex. These, in the method 

 of I>r. Leach, form three genera, but M. Latreille ii of opinion that 

 they may be united under one sub-genus, namely : 



(/bra (Leach; Axilofra, Weueira, of the aame). In those 

 Ouw/inr, designated by Dr. Leach u Olencinr, the blades of the fins 

 an narrow and armed with point* In those named by the same 

 aoolofbt .li/<x-nr the external blade of the fins is longer than the 

 infernal one ; the inrene of which is the case with the Canolira, in 

 which, besides, the eyes are but very little granulated, while they are 

 Tsry sensibly granulated in Anilocra. 



H. Latreille remarks that in the three following sub-genera the 

 second, third, and fourth feet only are terminated by a very strongly- 

 carred lail (onglet), and the but eight are spiny. The eyes ordi- 

 narily hare but little convexity, and are large and converging 

 anteriorly. 



OwoNr. (Anilatra) Qiftntlt. 

 jKya (Leach). Two first joints of the superior antenme very large 



.lift tmaifiutla. 

 , apjwr lids; , satrrlor foot ; r, posterior foot ; rf, under tide. 



Ratuulla (Leech). Two first joints of the superior antenna nearly 

 cylindrical, bat approaching the Afat in their Urge and anteriorly 

 approximated eye*. 



Owitfini (Leach). Antenna as in Kocinrl'.a ; but the eyes are small 

 and disUnt ; and the edges of the segment* are nearly straight, and 

 not falciform and prominent. 



Sfnediu < l.*tr.). Antenna upon two lines, lower antenna) always 

 nort, tail of aU segmtnU ; distinguished from all the preceding by 

 thrfr rmt and prfr^vf jawTonly one ipeoiei. 



ro/<ma (Leaeb). Length of the lower antenna surpassing the 

 half of that of the body. Six segment* in the tail. 



AWoc.ro (Leach). Length of lower antenna as in CVro/oao. Five 

 segments only in the tail Cornea of the eyes smooth. 



*""*!**_ (Leach). RoerobliDg \,loeira in the number of the 

 caodal segmetiU, but differing from that form in its granulous eyes. 



II. Latreille U of opinion that this sab-genus conducts as to those 

 whose eyes are formed of small grains, or which have those organs 

 mootb, and which have besides the four antenna; inserted upon tho 



AWwjra Stcaiiuonii, 



same horizontal line, consisting of four joints at moot, all the feet 

 ambulatory, and the tail composed of six segments. Such a form is 

 limnoria (Leach). The ouly living species known is L. tcrtbrani, 

 which, although only two lines in length, is nevertheless highly 

 injurious in consequence of its multiplication and its habits. The 

 rapidity with which this little crustacean pierces the timber of ships 

 makes its attacks not only mischievous but alarming. The pii-r at 

 Southampton and also that at Kerne Bay, have suffered from the 

 attacks of this crustacean. It rolls itself up like a wood-louse when 

 it is seized. It is a native of all the European seas. 



3. SPII.EUOMIDES (Latr.). The Jtopoda composing this section have 

 four very distinct antenna*, which nre either setaceous or conical ; and, 

 with the exception of Anlhura, they are always terminated by a stem 

 divided into many small joint*, and short. The lower air 

 which are always the longest, are inserted under the lower part of 

 the first joint, which is large and thick. The mouth has the usual 

 form. The branchiae ore vesicular or soft, naked, and disposed longi- 

 tudinally in pairs. The tail hag ouly two complete and moveable 

 segments, but has often impressed transverse lines upon it, indicating 

 the vestiges of other segments. On each side of its posterior extremity 

 is a tin terminated by two leaflets, the lower of which is moveable, 

 while the upper one is formed by an internal prolongation of the 

 common support The branchial appendages are curved internally ; 

 the internal side of the finst is accompanied in the males by a small 

 linear and elongated piece. The anterior part of the head, situated 

 below the antennae, is triangular, and in the form of a reversed heart. 

 Some have an oval or oblong body, contracting ordinarily into the 

 form of a bowl. The anteumc are terminated by a pluriarticulate 

 joint, and the lower ones at least are sensibly longer than the head. 

 The lateral and posterior fins ore formed of a peduncle and two blades, 

 composing, together with the hut segment, a fan-like fin. In them 

 the impressed and transverse lines of the anterior segment of the 

 tail, always shorter than its successor, or the last, do not reach the 

 lateral borders. The first joint of the superior antenna; is in the 

 shape of a triangular battledore (palette). The head seen from above 

 forms a transversal square. The leaflets of the fins are very much 

 flattened, and the intermediate piece, or last segment, is enlarged and 

 rounded laterally. 



Zuzara (Leach). Leaflets of the fins very large, the upper of 

 which is shortcut, separated from the other to form a border to the 

 last segment. 



Splueroma (Latr.). Leaflets of moderate size, equal, and applied 

 one over the other. 



Kfhirroma dnttata. 



Ill others the impressed lines, or transverse sutures of the anterior 

 segment of the tail, attain tho lateral border and cut it. The first 

 joint of the superior antenna; forms an elongated palette, which is 

 square or linear. The leaflet* of the fins are ordinarily narrower 



lidrntata. 



and thicker than in the preceding; the exterior sometime (ns in 

 Cymodocea) envelops the other : their point of junction resembles a 



