T R I 



[443 ] 



T R I 



gists ; some describe it as contain- 

 ing fluoric acid and alumina. 

 TEIA'NDEIA. (from rpci?, three, and 

 avrjp, a male, Gr.) The name of 

 the third class in Linnasus's sexual 

 system, consisting of plants with 

 hermaphrodite flowers, having three 

 stamens or male organs. This class 

 is divided into three orders: 1. 

 Monogynia. 2. Digynia. 3. Tri- 

 gynia. 



TEIAS, OE NEW RED SANDSTONE. (Some- 

 times called l Poikilitic? from the 

 prevalence of a variegated character 

 in its sandstones, and marls.) On 

 the continent where its several 

 members are better developed than 

 in England it has received the name 

 of 'Trias,' as divisible into three 

 great sub-divisions. The lowest 

 sub-division is the Bunter sand- 

 stone ; the second, or Muschelkalk, 

 is deficient in England ; the upper 

 is the Keuper marls, which contain 

 our great deposits of salt. Upon 

 the northern and southern flanks 

 of the Austrian Alps, at Hallstatt 

 and St. Cassian, are deposits of great 

 thickness, which are superimposed 

 upon the upper members of the 

 Trias, and are regarded as forming 

 a passage between the Trias and 

 the Lias ; the bone beds upon the 

 banks of the Severn at Westbury 

 and Aust are believed to be the 

 reduced equivalents of these great 

 deposits. Lycett. 



TEIA'SSIC. " This," says Mr. Jukes, 

 "is a very badly chosen name. The 

 triassic formation consists of the 

 Bunter sandstein, the Muschelkalk, 

 and the Keuper. In the British 

 Islands it is not easy to draw any 

 boundary lines in the Trias, or New 

 Red Sandstone." 



TEICA'PSULAB. A plant that has three 

 capsules to each flower. 



TEICHI'TES. The name assigned by 

 Mr. Lycett to a genus of fossil 

 inequivalve bivalves, whose struc- 

 ture is fibrous, the substance of the 

 test being of great thickness. The 



hinge is without teeth or hinge- 

 plate, and the anterior extremity 

 of the shell, which is pointed, forms 

 an aperture ; the general figure is 

 sub-quadrate, the valves being ir- 

 regular and undulated, but closing 

 all round. This singular genus 

 occurs in the oolitic system of rocks : 

 the absence of teeth, and the char- 

 acter of the terminal extremity 

 distinguish it from Catillus. 



TEICU'SPIDATE. Three-pointed. 



TEIDA'CNA. A genus of subtransverse 

 inequilateral, equi valve, marine, 

 bivalves, belonging to Lamarck's 

 family of Tridacnacea, and found 

 both recent and fossil. Recent 

 tridacna3 are found at depths vary- 

 ing to seven fathoms, moored by a 

 byssus to rocks, and on coral reefs. 

 The shells of this genus are ex- 

 ceedingly beautiful, being radiately 

 ribbed, the ribs adorned with vaulted 

 foliations, and waved at the margins. 

 The hinge is formed of two com- 

 pressed and entering teeth. One 

 species, the tridacna gigas, is met 

 with of immense size. Fossil shells 

 of this genus are very rare ; it is 

 said some large specimens have 

 been obtained from the neighbour- 

 hood of Yerona. 



TEIDA'CTYLOTJS. Having three toes. 



TEIGONELLI'TES. A genus of shells 

 described, and thus named, by Mr. 

 Parkinson. A slightly rounded, 

 trigonal, thick shell, gaping on 

 each side. The anterior margin 

 nearly on a straight line ; the pos- 

 terior in a gently waving, and the 

 upper side in nearly a circular 

 direction. The outer surface of 

 each valve thickly pierced by 

 foramina, which, passing nearly 

 through its substance, give it the 

 cancellous appearance of bone : the 

 inner surface smooth, but marked 

 with striaB, concentric with the 

 upper margin. Tlte hinge com- 

 pletely linear, without teeth ; there 

 being only an appropriate surface 

 on the anterior margin of each 



