ASTACID^E ASTARTE. 



227 



and muscles, and nerves, and membranous tissues, 

 and skin, and feathers, and scales, and horny beak 

 and claws ; all the organs which we afterwards 

 admire so much in that beautiful creature, which 

 sings from the spray, wheels swiftly through the air, 

 or rides gracefully upon the water. 



And all is effected by the power of assimilation, and 

 that too apparently without a point from which to 

 commence. Assimilation is thus totally different from 

 accretion or crystallisation. In these, new portions of 

 the same matter are merely added, without any 

 change ; but assimilation prepares a new material, 

 and either places it where there was no such material 

 before, or replaces with it other matter which has 

 ceased to be fit for the economy of the animal. See 

 GROWTH. 



ASTACID^E (Leach). A family of annulose 

 animals belonging to the class Crustacea, order Deca- 

 pod<i, and section Macrura, and containing the lobster 

 tribes. In this family the abdominal portion of the 

 body is much longer than the thorax. The eggs are 

 retained in a large pouch beneath the breast, the 

 first pair of legs are generally very large, and termi- 

 nated by hooks, claws, or a machine for swimming, 

 and the antennae, of which there are two pairs, are 

 inserted in the same horizontal line, the interior ones 

 with moderate or long footstalks, and terminated by 

 two filaments, and the outer ones naked or furnished 

 with a scale, which never entirely conceals the base. 



These characters will at once distinguish the lob- 

 sters from the hermit crabs (Paguridte), and prawns 

 and shrimps (PaleBmonidce). 



This family includes several distinct groups of 

 species, and we have also introduced into it the spiny 

 lobsters or cray fishes (Palimirus), which Dr. Leach 

 considered as forming a distinct family (PaUnurides), 

 chiefly from the small size of the fore-legs. These 

 animals, however, which are constantly sold by the 

 London fishmongers, are too closely allied to the 

 lobsters, as may be seen even upon a casual inspec- 

 tion, to warrant their establishment as a distinct 

 family, especially since we see, in the adjoining fami- 

 lies, amongst the shrimps, for instance, that the size 

 of the anterior locomotive organs becomes a charac- 

 ter scarcely of generic rank. 



The extremity of the abdomen is constantly fur- 

 nished with a fan-like apparatus for swimming, com- 

 posed of five plates, and the tegurnentary envelope of 

 the body is always of a hard and calcareous nature. 



The 1st sub-family, Scyllarides, is distinguished by 

 the remarkable construction of the lateral antennae, 

 which are much shorter than the thorax (which is 

 broad and flat), and instead of being slender, are di- 

 lated into very broad and flattened plates, having the 

 appearance of a cock's comb ; the fore-legs are 

 monodactyle and small, resembling the others, the 

 extremity of the caudal apparatus for swimming 

 is membranous. These Crustacea appear in warm 

 climates, some of the species being found in the 

 Indian and other tropical seas, whilst others are taken 

 in the Mediterranean ; the latter are known by the 

 name of Cigales de mer, which they probably owe to 

 the noise which they make in swimming : they bur- 

 row in clayey soils close to the shore. To this sub- 

 family belong the genera Scyllarus (Fabricius), of 

 which the Cancer arctus of Linnaeus may be consi- 

 dered the type ; Thenm (Leach), Scyllarus orientalis 

 (Fabricius), and Ibacus (Leach Ibacus Peronii), from 

 New Holland. 



The second sub-family, Palinnrides, resembles the 

 former in the simple fore-legs and the membranaceous 

 termination of the swimming plates, but the thorax 

 is convex, and not widened in front, and the lateral 

 antennae are very large, spinose, and much longer 

 than the whole body. One genus only, Palinuru.?, 

 (Fabricius), belongs to this division ; it includes some 

 of the largest of the macrurous (long-tailed) Crustacea, 

 and the species are in general of elegant colours. 

 They are termed langoustes by the French, a name 

 probably vulgarised from locusta, under which term 

 they were known to the Romans ; by the Greeks 

 they were denominated carabos, and Aristotle has 

 given various important observations upon their 

 natural history. It is singular that the common 

 species, in the west of Europe, although noticed by 

 all the old naturalists, should have been overlooked 

 by Linnaeus. This is the species of shell-fish sold in 

 our fish shops as the spiny lobster, and is highly 

 prized as an article of food. It is the Palnmrm qua- 

 dncorrns of Fabricius, the Cancer elephas of Fabricius, 

 the Palimirus locusta of Olivier, and the Palinurus vul- 

 gttris of Latrcille and Leach. During the winter it 

 seeks the deeper parts of the ocean, but at the return 

 of spring it approaches the shores, preferring rockv 

 situations where it deposits its spawn, which is of a 

 beautiful red colour. 



The third s.ub-family, TJialassinides, consists of 

 several interesting genera, of which the majority are 

 natives of our own coasts ; they are of small size, 

 and have much of the appearance of small lobsters, 

 the abdomen being long, and terminated by a 

 swimming apparatus of an entirely crustaceous sub- 

 stance ; the first pair of legs is terminated by large 

 claws, and the third pair is never furnished with a 

 two-fingered claw ; the exterior lamellae of the tail 

 are composed of one part only. This sub-family com- 

 prises the Indian genus Thalassina (Latreille), and 

 the British genera, Gebia (Leach), Cal/ianassa, 

 (Leach), and Ajcins (Leach). The latter are found 

 on the southern coasts of Great Britain, where they 

 burrow in the sand to a very considerable depth. 



The fourth sub-family, Astacides, have the abdomen 

 long, and terminated by scaly lamella? for swimming, 

 of which the exterior ones are bipartite. The fore- 

 legs are very large, each with a powerful claw, and 

 the four following legs are terminated by two-fingered 

 claws. This sub-family comprises the lobsters and cray- 

 fish ; of the former, the Cancer gammarus of Linnaeus, 

 which inhabits the rocky shores of our coast, is the 

 type of the genus Astacus of Fabricius, and the latter, 

 which Dr. Leach has formed into a distinct genus, 

 Potamobius, is found in all our fresh water streams. 

 Their food consists of decayed animal matter, and it is 

 with this, as a bait, that the majority of the vast numbers 

 which are annually consumed are caught. 



The LOBSTER, whose economy we shall detail under 

 that word, is distinguished generally from the cray-fish 

 by the middle lamella of the tail being composed of a 

 single piece, and by the sides of the abdominal seg- 

 ments being obtuse. 



The Cancer Norvegicus of Linnaeus, found on the 

 coast of Norway, is the type of the genus Nephrops 

 of Leach. 



ASTARTE (Sowerby). CRASSINA (Lamarck). 

 VENUS (Montague). This shell resembles a small 

 crassatella in appearance, being thick and solid, and 

 the valves perfectly closing together in every part ; 

 but the position of the ligament distinguishes it : nor 

 Y2 



