Snares of another type consisting of a tangled mass of threads amongst which the spiders pick their way with ease, but which are impassable to insects, are spun by members of the Theridiidae and Pholcidae; but by common consent the so-called orbicular web, so characteristic of the Argyopidae but by no means confined to them, is regarded as manifesting the greatest perfection of instinct in snare-spinning.
On account of its delicacy no web is more difficult to see than one of the orbicular type above described.
Perfect orbicular webs are made by many genera of Argyopidae (Zilla, Meta, Gasteracantha), the best-known example being that of the common garden spider of England, Aranea or Epeira diademata; but these webs are not associated with any tubular retreat except such as are made under an adjoining leaf or in some nook hard by.
Two genera of Argyopidae (Hyptiotes and Theridiosoma) construct spring-nets out of their incomplete webs of the orbicular type.
The number of eggs produced at a time varies enormously according to the species, from about half a dozen, more or less, in some ant-mimicking Attidae or jumping spiders to many hundreds in the larger orbicular-webbed spiders of the family Argyopidae.
Limopsidae.-Shell orbicular, hinge curved, ligament longer transversely than antero-posteriorly; foot elongate, pointed anteriorly and posteriorly.
Amussiidae.-Shell orbicular, smooth externally with radiating costae internally.
Pecten; shell orbicular, with equal auriculae; without a byssal sinus; British.
Dimyarian, with orbicular and almost equilateral shell; adherent; hinge without teeth Sand ligament internal.
Unicardiidae.-Shell sub-orbicular, nearly equilateral, with concentric striae.
Usnea, Peltigera); (b) lecanorine, or scutelliform, which are orbicular and surrounded by a distinct, more or less prominent thalline margin (e.g.
Thelotrema, Urceolaria); (c) lecideine, or patelliform, which are typically orbicular, with only a proper margin (e.g.
The form of the leaf shows a very great variety ranging from the narrow linear form with parallel sides, as in grasses or the needle-like leaves of pines and firs to more or less rounded or orbicular - descriptions of these will be found in works on descriptive botany - FIG.
Devon, is known as "orbicular silica" or "beekite," having been named after Dr Henry Beeke, dean of Bristol, who first directed attention to such deposits.
The bulbs are large and orbicular, and have a blackish coat; they, as well as the flowers, are reputed to be emetic in properties.