386 CRUSTAC 



Crustacea. Gr.xus XL. Galathea. Shell oblong-oval. 

 Family XI. Astacini. 



Tlie lateral caudal lamellae meeting the middle pro- 

 cess, and forming with it k fan-shaped fin. The inte- 

 rior antennae with a short peduncle, armed with joint- 

 ed setae. 



I. Feet ten. Hands didactyle. 



* Interior antennae with two setae. 



A. Antenna? placed in the same horizontal line. 

 Genus XLI. Astacus. Six anterior feet compound. 

 Genus XLII. Thalasina. Four anterior feet com- 

 pound. 



Genus XLIII. Upogebia. Two anterior feet com- 

 pound 



Genus XLIV. Callianassa. The four anterior feet 

 compound ; third pair monodactyle. 



B. Exterior antennae inserted below the interior ones, 

 with a large squama at their base. 



Genus XLV. Alph^us. The four anterior feet 

 compound. 



Genus XLVI. Pen^eus. The six anterior feet com- 

 pound. 



** Interior antenna? with three setae. 



Genus XLVII. Pal^emon. The four anterior feet 

 compound. 



II. Hands monodactyle, or with a moveable hook. 

 Genus XLVIII. Crangon. 



III. Feet more than ten. Hands simple. 

 Genus XLIX. Praunus. 



Family XII. Squillarii. 



Eyes pedunculated. The first joint in the body the 

 largest. 



Genus L. Squilla. Interior antennae with three 

 articulated setae. 



Genus LI. Mysis. Interior antennae with two ar- 

 ticulated setae. 



TRIBE III. GASTERURI. 



Eyfs sessile. The joint of the body Avhich receives 

 the head, of the same size with the rest. 



Family XIII. Gnathonii. 



Mandibules two, prominent. Antennae nearly equal. 

 Feet ten, all armed with a fixed nail. Tail with two 

 moveable plates on each side, forming, with a middle 

 process, a swimming tail. 



Genus LII. Gnathia. 



. Family XIV. Gammarini. 



Tail armed at its extremity with several styles. Feet 

 fourteen. Tail not distinct from the body. 



* Superior antennae shorter than the peduncle of the 

 inferior. 



Genus LIII. Talitrus. Anterior pair of feet largest. 



Genus LIV. Orchestia. Anterior pair of feet 

 smallest. 



** Inferior antennae shortest. 



Genus LV. Gammarus. The four anterior feet 

 equal, furnished with a moveable nail. Superior an- 

 tennae with a seta on the third joint of the peduncle. 



Genus LVI. Maera. Anterior feet with a move- 

 able nail, the second pair with a compressed hand and 

 moveable thumb. 



Genus LVIL Meuta. Anterior feet with a com- 

 ed hand furnished with a moveable thumb. 



< ienvs LVIII. Leucothce. Anterior pair of feet with 



FOLOGY. 



a finger and thumb, the second pair with a moveable Crustacea. 

 thumb. —" ~ V"" ' 



Family XV. Corophionii. 



Body elongated ; tail with four bifid styles ; feet four- 

 teen, anterior pair with a moveable thumb. The under 

 antennae as long as the body, (feet-like.) 



Genus LIX. Corophium. 



Family XVI. Caprellini. 



Body six-jointed ; all the articulations except the se- 

 cond and third bearing feet. Two oars on each side^ 

 placed on the sides of the second and third joint. 



Genus LX. Caprella. Body linear; oars globu- 

 lar. 



Genus LXI. Cyamus. Body depressed; oars elon- 

 gated. 



Family XVII. Apseudii. 



Body six-jointed ; tail also six-jointed ; the end arm- 

 ed with appendices. Feet fourteen ; the anterior pair 

 armed Avith a finger and thumb; second pair compres- 

 sed and denticulated. Inferior antennae bifurcated. 



Genus LXII. Apseudes. 



ORDER III. MYRIAPODA. 



Body, with seven or more feet-bearing articulations. 

 Antennae, filiform, two or four in number. Palpi, 

 single. Eyes, immoveable. 



The animals which compose this order were placed 

 in the class Arachnides, by Lamarck and Latreille; 

 but, from the characters we have given in the intro- 

 duction to this article, it is more correctly referable to 

 Crustacea. 



Observation. The animals of this order undergo no 

 transformation ; it has been stated, however, that some 

 of the Scolopendrides increase the number of their feet 

 during their growth : this Mr Leach denies, for, in his 

 cabinet, most of the indigenous species may be seen, 

 from the smallest size to the mature state, agreeing in 

 all points with full grown specimens. 



, TRIBE I. TETRACERA. 



Antennae, four or two in number. Feet, fourteen. 

 The anal segment of the body without feet, being some- 

 times armed either with lamellae or styles. 



Family XVIII. Asellides. 



Antennae generally very distinct, sometimes obscure ; 

 the internal or middle as long as the peduncle of the 

 external ones. The last segment of the body generally 

 largest. 



I. The four antennae very distinct. 



* The foliaceous appendices of the tail very large, 

 each one formed of a double scale ; the two scales par- 

 allel and meeting together. 



Genus LXIII. Asellus. Tail formed of one seg- 

 ment, with two bifid styles; the four antennae seta- 

 ceous, the outermost division being formed of a vast 

 number of little joints 



Genus LXIV. Idotea. Tail formed of two or 

 three segments, without styles; superior antennae fili- 

 form, having four great divisions, the outermost com- 

 posed of a great many smaller joints. 



* * Foliaceous appendices of the tail formed of one 

 or two processes, placed on a common peduncle situ- 

 ated on each side of the tail. 



