A C E P H A L O P H O II A A C E R I N E JE. 



23 



i-ra, or shell-bearing ; and the second tunicata, 

 or cloaked. 



ACEPHALA CONCHIFERA have the shell in all cases 

 external, and divided into two valves, which vary 

 much in their form, size, and mode of articulation. 

 (Javier divides thorn into families, each containing 

 many genera ; and the names of these families are as 

 follows: (htracesc (the oyster family), Miit'iliiccic 

 (the muscle family), Camacece (the chama family), 

 Cardiacefe (the cockle family), and Myece (the 

 family of gapers). 



MOLLUSCA TUNICATA. The members of this section 

 are in all cases without shells, the body being in- 

 vested with two cloaks or tunics, which are in some 

 instances separated from each other, excepting at 

 the natural openings of the animals"; while in others 

 they are united throughout their whole extent. In 

 some the surface is smooth, in others it is rough ; and 

 others again have the power of forming to themselves 

 a sort of artificial clothing by soldering or glueing all 

 over their bodies little pieces of sand and shells. 

 Some of them can move through the water by 

 first inflating the body with that liquid, and then 

 forcing it from the posterior aperture, by the 

 contractile force of the muscles of their tunics. The 

 anterior opening in the tunic is usually much larger 

 than the other one ; because, while in most, or 

 all of the conchifera, the gills are freely exposed to 

 the water as it passes between the open valves of the 

 shell, the gills of the tunicata are always within the 

 tunics ; and the animals either draw in water by the 

 mouth and puss it by the other opening, or inhale and 

 expel it by one and the same opening, in a manner 

 similar to the breathing of the cartilaginous fishes, and 

 not very dissimilar to that of the mammalia. 



The genera and species of this section are few, com- 

 pared with those of the former ; the following being 

 the principal : Thalia, Aacidia, Sotri/lliix, Pi/roxonui, 

 and I'olt/cl'uiuni ; the first and second having their 

 tunics separate, and the remaining three having them 

 united. 



Further particulars of the families composing the 

 first section, and the genera composing the second, 

 will be found under their respective names. 



ACEPHALOPHORA (Blainville). In the mo- 

 dern system of Malacology, an articulated molluscous 

 animal, in which the head is not distinct from the rest 

 of the body. It is without any sensitive apparatus. 

 The body is generally flattened, enveloped in a mantle, 

 divided into two lobes ; very rarely naked, and most 

 generally included in a bivalve shell. The mouth 

 large, constantly concealed, without any trace of teeth 

 or organs of mastication. The respiratory organs are 

 always bronchial or aquatic, and hidden. 



This class is divided into four orders. The 1st, 

 Pattiobranchiata ; 2d, Rudista ; 3d, Lamc.liihran- 

 rh'uila; 4th, Heterobranchiata ; descriptions of which, 

 with their divisions into families and genera, will be 

 given under their respective names, in the alphabetical 

 arrangement of this work. They embrace an extensive 

 and beautiful portion of that part of the inver- 

 toi>rutod animal kingdom called Conchology by 

 former naturalists, whose system was founded on 

 the Testaceous covering of molluscous animals, which 

 wholly covered, or only partially protected, certain 

 portions of their bodies, without any reference to the 

 structure and habits of the animal itself ; the only 

 natural and unerring guide in the study of this, as well 

 TV other work of the great Architect, of nature. 



All animals of this class are naturally aquatic : a 

 great number of them marine, but a few inhabit lakes 

 and rivers. They all feed on microscopic animals, or 

 animal substances, in nearly a molecular or extremely 

 minute state of division. 



ACER (the Maple). A family of hardy trees and 

 shrubs, chiefly natives of Europe and North America ; 

 belonging to the Linnaean class and order, Poli/gamia 

 Moncecia ; and to the natural order Arcr'nuc. Ge- 

 neric character : Calyx, more or less deeply divided 

 into five parts ; petals five ; stamens, generally five to 

 nine in number ; one style, two stigmas ; ovary de- 

 dymous ; leaves simple, opposite, and generally di- 

 vided into several distinct lobes ; seeds two, each 

 with a wing. 



This genus contains about thirty species and varie- 

 ties, and is arranged by botanists into four divisions, 

 founded on the form of the leaves as entire, and, 

 five-lobed, or cleft. They are all readily raised from 

 seeds, and also by layers, cuttings, and budding ; 

 directions for which operations, together with descrip- 

 tions of the more important species, will be given 

 under the article MAPLE. 



ACERA (Lamarck). Animals belonging to the 

 fourth order, Gasteropoda; second class, Pnraccpha- 

 Jophora, of Blainville's system of Malacology, fourth 

 family. The body more or less globose, gasteropod, 

 divided into two parts, the anterior of which is often 

 provided with lateral lobes ; the head indistinct, 

 without tentacula, or only with rudimental ones. 

 There is no internal or external shell. 



ACERINEvE (The Maple Family). The forty- 

 fourth order of the natural system of Jussieu, con- 

 taining two genera and fourteen species of valuable 

 forest-trees. They abound in North America, and 

 all over the North of Europe. The foliage is more 

 beautiful than the flowers, the latter being generally 

 small, and by no means showy. They all receive 

 the common name of maple, except the Acer pseudo- 

 platamis, which is called sycamore, and in Scotland 

 the plane-tree. The timber of almost all the species 

 is valuable for very many purposes ; especially to the 

 cabinet-maker, the turner, musical instrument-maker, 

 and for the manufacture of alkali, the maples of North 

 America, are of great value. The sap of all yields 

 sugar in considerable quantity ; the A. saccliar'mum 

 being the chief rival of the sugar-cane. For obtain- 

 ing this precious article in North America, Michaux 

 informs us that the following means are had recourse 

 to : In February or March, while the cold is still 

 intense, the bole of the tree is bored in two places, 

 five inches apart, at about twenty inches from the 

 ground, and on the south side of the tree. The 

 auger used should be somewhat more than half an 

 inch in diameter, and the holes are made in an 

 obliquely ascending direction, and to the depth of 

 half an inch into the alburnum or wood of the tree. 

 Into these holes tubes or fossets are fixed, ten inches 

 in length, to receive and conduct the sap into troughs, 

 placed below. The sap continues to flow pretty 

 copiously for a month or six weeks ; after which 

 time the flow declines. Four gallons of sap yield 

 about one pound of sugar, ami from two to four 

 pounds is the usual produce of a tree of the average 

 dimensions, and growing upon average soils. During 

 the sugar-making season, sheds are erected in the 

 wood, for carrying on the boiling and other pro- 

 cesses connected with the manufacture. Three 

 workmen are allowed to attend 1M trees, which give 



