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TUB 



like those in the tail of a lobster, and 

 generally divided by two longitudinal 

 furrows into three ranges of lobes. The 

 nearest approach among living animals to 

 the external form of trilobites is that 

 afforded by the genus serolis, in the class 

 Crustacea." 



TRILO'CULAR. (from tres, three, and locu- 

 lus, a partition, Lat. ) A term applied in 

 botany to seed-vessels divided into three 

 portions or cells. 



TRI'ONYX. (trionices, pi.) A subgenus 

 of testudo, belonging to the order Che- 

 Ionia. The soft-shelled tortoise. Two 

 species are mentioned, namely, ^Egyptia- 

 cus and ferox : the latter, or Trionyx 

 ferox, will attack, and master, aquatic 

 birds. The soft-shelled tortoises have 

 no scales, the shell and sternum being 

 merely enveloped in a soft skin ; many 

 of the pieces that are bony in the tortoise 

 being replaced by a simple cartilage or 

 membrane. Fossil remains of trionices 

 are found in fresh- water Wealden forma- 

 tions of the secondary series : one spe- 

 cies, named Trionyx Bakewelli, is de- 

 scribed by Dr. Mantell, as occurring in 

 Hastings beds. Remains also are abun- 

 dantly found in the lacustrine deposits of 

 the tertiary formations. 



TRI'POLI. An admixture of silex and clay. 

 It has obtained its name from having 

 been originally brought from Tripoli, in 

 Barbary. It is a mineral of a dull ar- 

 gillaceous appearance, occurring usually 

 in friable or earthy masses. Its powder 

 is fine, but dry and rough to the touch, 

 and sufficiently hard to scratch metals, 

 glass, &c. It is employed for the polish- 

 ing of metals and stones. Rotten-stone 

 and polishing-slate, the Polierschiefer of 

 Werner, appear to be varieties of Tri- 

 poli. 



TRISE'PALOUS. (from tres, three, and 

 sepal.) A term used in botany for a 

 calyx that has three sepals. 



TRI'TON. A genus of the molluscous order 

 of Nudibranchiata, inhabiting an oblong, 

 thick, ribbed, or tuberculated spiral shell. 

 The body is oblong ; mouth with an in- 

 volute spiral proboscis ; tentacula twelve, 

 six on either side, divided nearly to the 

 base, the hind one cheliferous. 



TROCHI'TA. A detached vertebra of a 

 radiated animal. When several trochitae 

 are united, so as to form part of a 

 column, the series is termed an entro- 

 chite. 



TRO'CHUS. (trochus, Lat. a top.) A 

 genus of conical, spiral, thick, striated, 

 marine, univalves, found both fossil and 

 recent. The animal is a Limax ; aperture 

 transversely depressed, and somewhat 

 quadrangular ; columella oblique ; oper- 

 culura horny, with numerous whorls. 



Recent trochi are found in the ocean at 

 depths varying to forty-five fathoms ; 

 they most commonly, however, are met 

 with near the shore, creeping on rocks, 

 sands, and gravel. One hundred and 

 thirty-three species are described in Tur- 

 ton's Linne. Lamarck has separated 

 from the genus trochus of Linnaeus cer- 

 tain shells possessing peculiar characters, 

 which he has arranged under two new 

 genera, namely, Solarium and Mono- 

 donta. These genera, as well as tro- 

 chus, are comprised in the family Turbi- 

 nacea. 



Of fossil trochi, Dr. Mantell enu- 

 merates six species as occurring among 

 the Sussex fossils. One species in dilu- 

 vium, one in the London clay, one in the 

 chalk, two in the chalk-marl, and two in 

 the upper green-sand. Very large casts 

 of trochi are found in Oxfordshire, Glou- 

 cestershire, and Somersetshire. 



TRO'PHI. The name given by Kirby and 

 S pence to the elementary parts which 

 enter into the composition of the mouth 

 of an insect. 



TRU'NCATED. (truncatus, Lat.) Cutoff; 

 shortened. 



TRUNCATION. A term used in mineralogy, 

 implying that a segment is cut off or 

 separated from the predominant form. 

 The term may be applied either to an 

 edge, or a solid angle of a crystal, and 

 will leave a face more or less large in 

 place of the edge or angle. A truncation 

 is said to be oblique, when the face does 

 not make equal angles with all the conti- 

 guous faces. Cleaveland. 



TUBE, (tubiis, Lat. tube, Fr. tubo, It.) 

 A pipe ; a siphon. In botany, the round 

 hollow part of a monopetalous flower. 



TU'BER. In botany, a fleshy irregular 

 stem produced under ground, and distin- 

 guished from a root by its having eyes 

 or buds, which the true root never 

 possesses : the potatoe is a familiar ex- 

 ample. 



TU'BEROUS. (tubereux, Fr. tuberoso, It.) 

 Having prominent knots or excrescences. 



TUBICINE'LLA. (from tubicen, Lat. a trum- 

 peter.) A genus of multivalve tubular 

 shells, not spiral. Tubicinella is placed 

 by Lamarck in the order Sessile cirri- 

 pedes. The tube is cylindrical, and com- 

 posed of six elongated valves, laterally 

 united. The aperture circular, with a 

 four-valved operculum. Tubicinellse are 

 not described as occurring fossil ; the 

 recent are found imbedded in the blubber 

 of whales. 



TUBI'COLA. (from tubus, a tube, and cola, 

 an inhabitant, Lat.) An order of Arti- 

 culata, comprising Serpula, Sabella, Te- 

 rebella, Amphitrite, Syphostoma, and 

 Dentalium. 



