188 ARBUTUS- 



there are ten species, natives of Europe, Asia, and 

 other parts of the world. Linnaean class and order, 

 Mimcccia Monadelphia ; natural order, Conifers. 

 Generic character: male flower, catkin small and 

 round ; anthers four, sitting, somewhat globular and 

 scaly at the base. Female flowers scaly, digy- 

 nous at the top ; embryo having two seed-leaves. 

 These trees are usually planted in pleasure grounds, 

 and answer the purpose of shrubs rather than trees, 

 as they give depth and density to ornamental planta- 

 tions. Like othersof the coniferous tribe, they always 

 add a richness to dressed scenery, whether standing 

 alone on the lawn, or intermixed with other trees. 

 Propagated by seeds. 



ARBUTUS (Linnaeus). Strawberry-tree. A genus 

 of beautiful evergreen shrubs, natives of Ireland 

 and South America, belonging to the Liuneean 

 class and order, Decandria Monogynia ; natural order, 

 EricecE. Generic character: calyx, five cleft ; corolla, 

 pitcher-shaped, limb with five reflexed teeth ; stamens 

 inserted on the base of the corolla ; filaments short, 

 dilated at the base ; anthers, two celled, opening by 

 two pores at top, on the back a bristle ; germen, disk 

 ten angled ; style, simple ; stigma obtuse ; berry of 

 five cells, containing many seeds. Whether while 

 in flower or in fruit, no shrub is more ornamental 

 than the Arbutus uncdo being both an elegant and 

 hardy plant, showing to particular advantage in the 

 months of October and November, when it is covered 

 at once with blossoms and fruit. In Ireland it is 

 found wild, growing on limestone rocks in greater 

 luxuriance than in Italy. 



ARC A (Linnaeus, Lamarck, Cuvier). Fifth family, 

 Potyodonta ; third order, Lamellibranchiata ; third 

 class, Acephaloplwra ; of De Blainville's System of 

 Malacology. The body of these mollusks is thick, of 

 rather a variable form ; the abdomen provided with 

 a pedunculated foot, compressed fitted for adhesion, 

 and divided lengthways ; the mantle provided with 

 a single row of cirrhi prolonged rather backward; the 

 buccal tentaculae very small and very rough. 



The Arcacae, as they are now established by modern 

 naturalists, present a numerous and well defined 

 genus, easily recognised by their general resemblance 

 to the hull of a ship, whence they have derived their 

 name, and by which they are distinguished from 

 their congeners. The Linmean genus Area 'is very 

 properly subdivided into three, Area, Pectunculus, 

 and Nucula ; Lamarck made another, which he called 

 CucullfEft; but it is restored by De Blainville to the 

 arks ; each of these genera possesses a strong distinc- 

 tive character, fully sanctioning a separation from 

 each other. 



The shells of this genus are transverse, subequi- 

 valve, inequilateral ; the apices distant and separated 

 by the angular area or channel of the ligament, which 

 is always external ; the hinge is placed in a right 

 line in most species ; they are without ribs and fur- 

 nished with numerous small sharp teeth, alternately 

 inserted between others in the opposite valve ; in 

 many species the valves when shut, gape in the centre, 

 occasioned by the wide flexuous curve of their outer 

 margins, and sometimes one valve overlaps the other. 

 They are said to spin a byssus, and are covered with 

 a lamellar or velvet like epidermis, frequently ending 

 in a deep fringe. The valves are longitudinally 

 ribbed, imbricated, smooth, granulated, or finely 

 striated. 



De Blainville has divided the genus into six spe- 

 cies j the first navicular with the hinge completely 



A R C T O M Y S. 



straight, the foot tendinous and adherent, as in the 

 Area Note, here figured ; the second species is twisted. 



Area Nose, 



close shutting, and the hinge quite linear, as in the A. 

 tortosa ; the third boat-shaped, with a straight hinge, 

 and the terminal teeth longer arid more oblique than 

 the others, A. auriculifera, constituting Lamarck's Cu- 

 culltEa, so named from each valve possessing a small 

 chambered portion or hood-like separation ; the fourth 

 species has a straight hinge, but it is not notched or 

 gaping beneath, and the muscle of it is not adherent, 

 A. barbata; the fifth species is perfectly close, they 

 are of a less elongated shape, more pectiniform, and 

 with a straight hinge; and the last division includes 

 all that are elongated, a little arched lengthways, 

 slightly gaping beneath, the summits much closer, 

 the ligament nearly interior, and the dental line a 

 little arched, A. mytiloidea. 



Area Barbata. 



Lamarck enumerates thirty-seven recent species 

 and nine fossil. De France mentions twenty-five 

 fossil species, besides three of Cucullcea. They inhabit 

 the sea in all parts of the globe, at a short distance 

 from the shore ; and, though not particularly distin- 

 guished for the richness of their colouring, they are 

 many of them beautifully sculptured and of a very 

 graceful form. 



ARCHANGEL. The English name of a family 

 of herbaceous annual and perennial plants, several of 

 them indigenous to Britain, but not in cultivation. 

 They are sometimes called " dead nettle" from their 

 appearance, yet harmless character. Two of them, 

 Lamium orvala and L.flexuosum, are admitted into 

 the flower borders, but they are exotics. 



ARCTOMYS Marmot. A genus of mammalia 

 belonging to the order of rodentia or gnawers. 

 Like the rest of the order they are without canine 

 teeth, and in the sharpness of the incisors of the 

 lower jaw they bear some resemblance to the great 

 family of rats and mice, of which perhaps they may 

 be considered a sa subdivision, though, in some re- 

 spects, they bear at least a slight resemblance to the 

 squirrels, and their external, forms and also their man-. 



