120 



ANODONTA. 



upon the one or the other, are generally superior in 

 flavour to those which feed on vertebrated animals, 

 and especially to those which feed upon radiated 

 animals, many of which are understood to give poi- 

 sonous qualities to the fishes that feed upon them. 



The annellidse are, from the structure of their 

 breathing apparatus, readily divisible into three 

 orders, Tubicola, Dorsibranchia, and Abranchia. 



TUBICOI.A. These, as the name imports, inhabit 

 tubes or pipes. Sometimes the tube is calcareous, 

 of a structure tolerably uniform, though coarse and 

 bearing some resemblance to the shells of mollusca; 

 but in no case is it united to the body of the animal 

 by any muscular or tendinous connexion. Tubes 

 of this kind are generally understood to be formed of 

 a sort of secretion or exudation, furnished by the 

 body of the animal, but by what part of it has not 

 been ascertained. The tubes of these often proceed 

 by curious convolutions and ramifications along the 

 surface of submarine stones ; they are not found in 

 fresh water. Other species unite together by a sort 

 of cement, grains of sand, little pieces of mud, and 

 portions of shells ; and there are some which con- 

 struct for themselves membranous tubes, formed 

 entirely of flexible or horny substance, but their 

 bodies are not more united to these, than when 

 the tubes are chiefly composed of foreign sub- 

 stances. The animals of this order have the breath- 

 ing apparatus in the form of small plumes of feathers, 

 or minute branches of trees, exquisitely ramified, and 

 attached to the head or to the anterior part of the 

 body. 



DORSIBRANCHIA. These have the breathing ap- 

 paratus spread over the surface of the body in the 

 form of brooches, rings, scales, or tubercles. A small 

 number of them live in tubes ; but by far the greater 

 part either live naked in the mud or swim freely in 

 the water. All the species of the two orders now 

 mentioned have their sides furnished with small 

 bristles, stiff, and having a metallic lustre, some- 

 times single, and sometimes in little clusters or 

 tufts ; these bristles are to be considered as their 

 organs of locomotion, whether along hard sub- 

 stances, through the ooze and mad, or through 

 the water. 



ABRANCHIA. The animals of this order have 

 not, as the name imports, any external organs of 

 respiration that are apparent to common observa- 

 tion. Those which inhabit the earth, and of which 

 the internal breathing apparatus must be considered 

 as lungs, appear to breathe with the whole surface of 

 the body, or at least by means of minute pores gene- 

 rally distributed over the surface. Those which in- 

 habit the water and have the internal breathing 

 apparatus, as gills, appear to breathe by receiving 

 water into the internal cavities. This order admits oi 

 a very obvious division into two families : those which 

 have the rings furnished with bristles, and those 

 which have them without. Some of the first inhabit 

 the land, and the most familiar type is the common 

 earth-worm ; and the others of that family mostly in- 

 habit fresh water, and one species at least live in 

 tubes. These move on by the action of their bristles ; 

 but they can move; for some distance at least, with 

 either end foremost, as may be seen in the case oi 

 the common earth-worm, which, if it has the least bit o 

 the tail in its hole, can speedily draw in the whole body 

 The common leech is an example of the seconc 

 family, the members of which are chiefly aquatic 



.hey move along solid surfaces by means of their 

 suckers ; and through the water by flexures of the 

 >ody. See LUMBRICUS, HIRUDO. 



ANODONTA, or more correctly ANODON. 

 'Lamarck) ; MYTILUS, (Linnaeus). A genus of 

 molluscous animals belonging to the class Acejyhalo- 

 phnra ; order Lamellihranclriata, arid family Submy- 

 tilncca of De Blainville's Malacology. The body of 

 this shell is rather thick, slightly compressed, more 

 or less oval ; the mantle, with thick edges, plain or 



Anodon Dipsas. 



fringed, open the whole length of the circumference, 

 except towards the back, a distinct oval orifice for 

 the vent ; a species of little tube, incomplete and 

 fringed with two rows of rather long oirrhi, forming 

 the respiratory cavity ; the fooflamelliform and sharp. 

 The shells of this genus have been separated from 

 the Linnsean Mytili, with which however they are so 

 nearly allied that it requires a careful examination of 

 the hinge to distinguish them from each other ; this 

 genus, however, wants the cardinal and lateral teeth, 

 and merely presents a smooth internal rim round the 

 edge, whence it has very characteristically been 

 named Anodon, from , not, and <&ou;, a tooth (having 

 no tooth) ; this rim is terminated at the anterior end 

 by a sinus or notch, in which the anterior extremity 

 of the ligament is sunk or attached. This species 

 of shells is usually eroded or rubbed by the fre- 

 quent opening and shutting of the valves, which 

 takes place while in the act of feeding or removing 

 from one spot to another. The substance of the 

 shell is pearly (and some of the species produce 

 pearls) ; it is covered with a false epidermis ; the 

 valves are generally thin and concave, they occa- 

 sionally attain a considerable size ; the valves are 

 similar in size, transverse, inequilateral, with two 

 distinct internal muscular impressions, the ligament 

 external, insinuated at the anterior extremity into the 

 sinus of the cardinal ridge. 



They inhabit ponds and lakes in every part of 

 the globe, particularly in North America, and the 

 animal is supposed to be viviparous ; that is, to bring 

 forth its young alive. 



De Blainville divides this genus into five species : 

 the first, such as are thin, oval, much elongated, not 

 oared, the hinge very long, straight, and crenulated 

 its whole length, as in the Anodon exotica, which forms 

 Lamarck's genus Iridina ; the second species are 

 oval, with the hinge arched, and without any trace of 

 ears, as in the A. rubens; the third species are oval or 

 elongated, a linear hinge, and oar-shaped at the ante- 



