GLOSSARY. 475 



TECTIBRANCIIIA'TA, an order of mollusks, in which the gills are 

 concealed under the fold of a mantle, as in the Aplysia or 

 Sea-hare. Lat. tectus, covered or protected, and branchice, 

 gills. 



TENTACULA, retractile organs surrounding the mouth, and used 

 by many aquatic animals for seizing their prey. 



TERRESTRIAL, connected with or relating to the earth. Lat. 

 terra, the earth. 



TERTIARIES, the feathers in the wings of birds which grow on 

 the humerus, or bone corresponding to that between the 

 elbow and the shoulder. 



TERTIARY ROCKS, " a series of sedimentary rocks with charac- 

 ters which distinguish them from two other great series of 

 strata the secondary and the primary which lie beneath 

 them." LYELL. 



TESSELATED, divided into squares. The term is applied to a 

 pavement formed of square- shaped stones, often of different 

 colours. Lat. tessera, a square tile. 



TESTACEA, mollusks with a shelly covering, such as the Snail, 

 the Whelk, the Oyster. Lat. testa, a shell. 



TESTUDINA'TA, that order of Reptiles which includes the Tor- 

 toises. Lat. testudo, a tortoise. 



THORAX, the chest. In the true insects, the organs of locomo- 

 tion, whether wings or legs, are attached to the thorax. 



TIIYSA'NOURA, an order of apterous or wingless insects, which 

 have the tail fringed with numerous minute hairs. Gr. 

 thysanoi, fringes, and our a, the tail. 



TORPIDITY, that state of rest observable in the hybernating 

 animals, in which they remain without exerting any of the 

 powers of active life, and with diminished animal heat and 

 respiration. In many cases the word implies benumbed with 

 cold. 



TRACHE'A, the wind-pipe. 



TRANSFORMATION, the changes which animals undergo in their 

 progress from the ovum or egg state, until they assume the 

 appearance of the perfect animal. 



TRANSITORY, continuing but a short time. 



TRANSLUCENT, permitting the light to pass through. Lat. 

 translucere. 



TRANSVERSE, across, being in a cross direction. Lat. trans- 

 versus, from transvertere, to turn across. 



TRILO'BITES, a tribe of extinct crustaceous animals, so called 

 from the body being composed of three lobes. 



TRIPOLI, a powder used for polishing metals and stones, first 

 imported from Tripoli. It is composed in a great degree of 

 the flinty cases of Infusoria. 



TRIPOD, with three feet, or resting on some support of an analo- 

 gous kind. Gr. treis, three, and pous, a foot. 



TRIRADIATE, arranged in the manner of three radii, or lines 

 proceeding from the same centre. 



TUBERCLES, small pimples, or similar excrescences, giving a 

 rough or warty appearance to the surface. 



