1093 



TRIDACNID.E. 



TRIFOLIUM. 



1094 



posterior and inferior for the anus and for regpiration, the third 

 anterior, corresponding with the gape of the lunule, and giving passage 

 to a thick, cylindrical, and byssiferous foot, in nearly all the 'species. 

 Mouth oval, furnished with great lips, at the extremity of which are 

 two pairs of pointed labial palps. (Deshayes.) 



Shell regular, equivalve, inequilateral, transverse ; with a gaping 

 lunule. Hinge with two compressed, unequal, anterior, and intrant 

 teeth. Ligament marginal, external. (Lamarck.) 



T. gigaa. Shell very large, transversely oval, with great imbricate 

 squamous ribs, the scales shot, arched, and lying near together ; the 

 interstices of the ribs not striated. 



Tridacna yiynt. 



TriAacnn hippoput. 



The size and weight of this immense bivalve, the largest and heaviest 

 known,* combined with the beautiful marble-like appearance and 

 whiteness of the inside of the valves, have always caused it to be 

 sought for as an ornament for grotto-work or for garden-fountains ; 

 and, indeed, the valve of a large individual forms a very picturesque 

 basin for catching the clear falling water and transmitting it through 

 the deep interstices of its indented edge to the reservoir below. 

 Wolfart's fossils were not improbably the relics of some ancient and 

 long-neglected pleasure-ground. Tbe specimen whose valves serve for 

 holy-water vessels (Bduitiers) in the church of Saint Sulpice was 

 presented to Francis I. by the republic of Venice; and Lamarck 

 observes that, large as these are, still larger have oeeu known. 



This species can hardly have been the Tridacna of Pliny ('Nat. 

 Hist.,' xxxii. 6), which was probably only some overgrown European 

 oyster that required three bites. A fine well-fed Indian giant Tridacna 

 would furnish forth a dish for a dozen. But it is not improbable 

 that the Pedalia, or oysters a foot long, from the Indian Sea, noticed 

 in the preceding sentence of the same book and chapter, may have 

 been Tridacna of modern authors. 



The figure of T. gigai given in the 'Zoology of the Astrolabe" was 

 designed at Carteret Harbour, New Ireland. The natives brought 

 many very large individuals, whose flesh was abandoned to them, and 

 which they ate raw. The naturalists of the expedition found the 

 species again at Tongataboo, at the Moluccas, at Timor, and at Wagiou. 

 It appeared always to inhabit rather shallow water. 



Some fine specimens are to be seen in the Garden of the Zoological 

 Society, Regent's Park. 



T, hippopua (Chama hippopus, Linn.; Hippopus muculatus, Lam.; 

 Tridacna maculata, Quoy, ' Voyage of the Astrolabe.') 



This well-known but beautiful species, now much used in the orna- 

 mental arts for inkstands, &c., has a transversely ovate shell, which is 

 of moderate size, ventricose, ribbed, subsquamous, and white spotted 

 with red or purple ; the lunule is heart-shaped and oblique. 



The naturalists of the 'Voynge of the Astrolabe ' found this species 

 at Carteret Harbour, New Ireland, and also at Vanikoro, where they 

 collected specimens left dry on the reefs. 



TRIDACOPHYLLIA. [MADREPHYLLHEA.] 



TRIDACTYLUS, a genus of Orthopterous Insects, belonging to the 

 family Gi-yllid<e. They are minute exotic insects, fossorial in their 

 habits, using the anterior tibuc. The posterior tarsi are replaced by 

 narrow bent moveable appendages. The antennae are very short, and 

 10-jointed. 



TRIENTA'LIS, a genus of Plants belonging to the natural order 

 Primulacea. In British botany thia genus is somewhat conspicuous, 

 as it is the only one which belongs to the Linmean class ffeptandria. 

 The parts of the fructification are remarkable for being arranged 

 according to the number seven. 



T. Europaa, the European Chick- Weed, Winter-Green, is a British 

 species. It is distinguished from the American species by possessing 

 elliptical instead of lanceolate leaves. This plant is rare iu England, 

 being only occasionally met with in woods iu the northern counties ; 

 't is however abundant iu many parts of the Highlands of Scotland. 



T. Americana, the American Chick- Weed, Winter-Green, has lanceo- 

 late leaves. It is found in mountainous districts in Canada and 

 Virginia. 



TRIFO'LIUM (Tpl<t>u\\ov), a genus of Plants belonging to the 

 natural order Leguminosce. This genus, which has obtained its Latin 

 as well as its French and English designations, Trefle and Trefoil, from 

 its leaves possessing three segments, is one of the most extensive in 

 the vegetable kingdom. The calyx is tubular, 5-cleft ; corolla remaining 

 after decay ; carina obtuse ; stamens diadelphous, more or less connate 

 with the petals, the filaments dilated above; the style smooth ; legume 

 ovate, with one or two seeds, sometimes oblong, with three or four 

 seeds, and included within the decaying calyx and corolla. All the 

 species are herbs. The leaves are mostly divided into three segments or 

 'oliolules ; sometimes they are seen with four or five. The flowers 

 are disposed in dense heads or spikes, and are of a purple white or 

 ream-colour. De Candolle has arranged the numerous species of this 

 jenus under seven sections, the characters of which are founded princi- 

 pally on the inflorescence and on the form of the calyx, or of the corolla 

 iombmed with it. We shall here select some of the most useful and 

 remarkable of the species as illustrations of the genus. 



T. incarnatum, Flesh-Coloured Trefoil, or Scarlet Clover. The spikes 

 of flowers are at first ovate, at length cylindrical, solitary, and naked 

 at the base; the calyx 10-nerved and hairy, with unequal awl shaped 

 acute teeth, longer than the tube and shorter than the corolla ; stipules 

 ovate and obtuse ; leaflets obovate, crenated, villous ; stem erect. The 

 species i a native of the south of Europe, in damp meadows. [ClovER, 

 u ARTS AND Sc. Div.] 



T. anense, Hare's-Foot Trefoil The stem erect, branched, or simple; 

 lends of flowers very hairy, soft, nearly cylindrical, terminal, stalked ; 

 ,he teeth of the calyx longer than the corolla, setaceous, and some- 

 what spreading ; stipules ovato-acuminate ; leaflets lanceolate, obtuse. 

 This plant is a native of Europe, and is abundant in corn-fields and dry 

 lastures in Great Britain. Its soft hairy subcylindrical heads or spikes 

 five it a very remarkable character. 



T. maritimum, Sea-Side or Teasel-Headed Trefoil. The heada are 



* Five hundred pounds have been recorded as its -weight. 



