THE 



303 



THE 



3. Thebes, in that part of Arabia Felix which was 

 called the country of the Cinaedocolpitae. 



4. Thebes in Lucania in Italy. ( Pliny, Hist. Nat., iii. 

 15.) Stephanus of Byzantium (s. v. 6ij/3m) mentions seve- 

 ral other towns of this name, of which however nothing 

 is known. 



THECA, a term in vegetable anatomy. It was applied 

 by Grew to that part of the stamen which contains the 

 reproductive granules and which is now generally called 

 the anther. [ANTHER.] It is also extensively employed in 

 cryptogamic botany. Among the ferns, it is applied, 

 in common with the terms capsule, conceptacle, and 

 sporangium [SPORANGIUM], to those little granules which 

 constitute the masse.-; called sori. In the Equisetacese it 

 expresses the assemblage of cases, which are attached to 

 scales arranged in a conical manner. 



The same term is used to indicate the kidney-shaped 

 two-valved cases that contain the reproductive matter of 

 Lyeopodiaceae and also the urn-like organs that enclose the 

 sporules of mosses. It is by some writers still further ex- 

 tended, and used to express the parts that contain the 

 sporules in Lichens and Fungi. 



THECA 'in Anatomy j is a term commonly applied to 

 the strong fibrous sheaths in which certain soft parts of the 

 body are enclosed. Thus the tkeca vertebra/if is the 

 sheath of dura mater in which the spinal chord is enclosed ; 

 and the canals through which many of the long tendons 

 of the muscles of the hand and foot run are called thecse. 

 These last are always lined by a synovial membrane, and 

 contain a small quantity of fluid [SYNOVIA], by which the 

 sliding of the tendons is facilitated. 



THECADAGTYLS, Cuvier's name for those 6><7/v 

 which have the toes enlarged throughout their length, and 

 furnished below with transverse scales, which arc divided 

 by a longitudinal furrow, where the claw may tie entirely 

 hid. [GECKO.] 



THKCIT)EA, or THECITJIUM. [BRACHIOPODA, vol. 

 v., p. 313.] Mr. J. E. Gray arranges the Thecideidte as 

 the fourth family of the Brachinpodn, placing it between 

 the l'i and the Cruniadie, and making it consist 



of the single genus Thecidea. 



THECODO.NTOSAU'RUS. [THECODONTS.] 



THECODONTS. Professor Owen, in his ' Report on 

 li Fossil Reptiles,' observes that among the inferior 

 or squamate saunans there are two leading modifications 

 in the mode of attachment of the teeth, the base of which 

 may he either anchylosed to the summit of the alveolar 

 ridge, or to the bottom of an alveolar groove, and supported 

 by its lateral wall. These modifications are, he remarks, 

 indicated respectively by the terms 'acrodont' and ' pleu- 

 rodont.' A third mode of fixation is presented by some 

 extinct saurians, which, in other parts of their organiza- 

 tion, adhere to the squamate or lacertine division of the 

 order, the teeth being implanted in sockets, either loosely 

 or confluent with the bony walls of the cavity : these 

 ssor Owen has, in his ' Odontography,' termed the 

 '/'//'-' riiitns, the most antient of all saurians be- 



longing to this group. 



Commencing with the Tkecodontotaurut of Dr. Riley 

 and Mr. Stutchbmy, described by them in the ' Geological 

 Transactions ' of 1836, from remains found in the dolomitic 

 conglomerate of Redland, near Bristol, the oldest or lowest 

 division of the new red sandstone series, Professor Owen 

 remarks that this reptile is allied to the typical Varanian 

 Monitors, but differs from them in having the teeth im- 

 bedded in distinct sockets; but that the / "urn/ii, among 

 the squamate saurians, approach to this condition in the 

 shallow cavities containing the base of their teeth along 

 the bottom of the alveolar groove. 



But, in the extinct genus now under consideration, the 

 sockets are, he states, deeper, and the inner alveolar wall 

 is nearly as high as the outer one ; the teeth are arranged 

 in a ' -.lightly decreasing in size towards the 



posterior part of the jaw ; each branch of the lower jaw 

 is supposed to have contained twenty-one teeth, which are 

 conical, rather slender, compressed and acutely pointed, 

 with an anterior and posterior finely serrated edge, the 

 lerratuifs being directed towards the apex of the tooth, as 

 ;n G. i It/iopa lotion ; the outer surface is 



more convex than the inner one ; the apex is slightly re- 

 curved : and t: | the crown contracts a little to 

 form the subcyiindrical fang. He then goes on to remark 

 lhat the pulp-cavity remains open in the base of the 



crown ; that, in their microscopic structure the teeth of 

 the Thecodontosaurus closely correspond with those of 

 Varanus, Monitor, and Megalosaurus ; that the body of 

 the tooth consists of compact dentine, in which the cal- 

 cigerous tubes diverge from an open pulp-cavity at nearly 

 right angles to the surface of the tooth ; that they form a 

 slight curve at their origin, with the concavity directed 

 towards the base of the tooth ; then proceed straight, and, 

 at the periphery, bend upwards in the contrary direction. 

 The diameter of the calcigerous tube he gives as l-30,000th 

 of an inch, and the breadth of the interspace of the tube 

 as l-8000th of an inch. The crown of the tooth is in- 

 vested with a simple crown of enamel. This microscopic 

 examination, which Professor Owen was enabled to make, 

 by the kindness of Mr. Stutchbury, satisfactorily esta- 

 blishes, in the Professor's opinion, the distinction between 

 the saurian of the Bristol conglomerate and Labyrinthodon. 

 [SALAMANDROIDES.] 



Of PAL^EOSAURUS Professor Owen states that its tooth 

 is compressed, pointed, and with trenchant serrated mar- 

 gins ; but that its breadth, compared with its length, is 

 much greater than in Thecodontosaurus. The vertebrae 

 associated with these teeth were biconcave, with the, 

 middle of the body more constricted, and terminal arti- 

 cular cavities rather deeper than in TELEOSAURUS ; but, 

 the Professor adds, they are chiefly remarkable for the 

 depth of the spinal canal at the middle of each vertebra, 

 where it sinks into the substance of the centrum, and thus 

 the canal is wider vertically at the middle than at the two 

 ends of the vertebra : an analogous structure, he observes, 

 but less marked, obtains in the dorsal vertebrae of the 

 Rht/nchosaurun from the new red sandstone of Shrop- 

 shire. 



Professor Owen then points out that besides deviating 

 from existing lizards in the thecodont dentition and bicon- 

 cave vertebrae, the antient saurians of the magnesian con- 

 glomerate also differed in having some of their ribs arti- 

 culated by a head and tubercle to two surfaces of the 

 vertebra, as at the anterior part of the chest in Crocodiles 

 and Dinosaurs. The shaft of the rib, he tells us, was tra- 

 versed, as in the Ichthyosaur and Rhynchosaur, by a deep 

 longitudinal groove ; and some fragmentary bones indi- 

 cut id obscurely that the pectoral arch deviated from the 

 Crocodilian, and approached the Lacertian or Enaliosau 

 riau type in the presence of a clavicle, and in the breadth 

 and complicated form of the coracoid. The humerus, h 

 observes, appears to have been little more than half the 

 length of the femur ; and to have been, like that of the 

 Rhynchosaurus, unusually expanded at the two extremi- 

 ties. 



After quoting the description of the femur by the dis- 

 coverers of the present thecodont reptiles, Professor Owen 

 remarks that the tibia, fibula, and metatarsal bones mani- 

 fest, like the femur, the fitness of the thecodont saurians 

 for progression on land. The ungual phalanges, he ob- 

 serves, are subcompressed, curved downwards, pointed, 

 and impressed on each side with the usual curved canal. 



The Professor draws the following conclusions from the 

 knowledge at present possessed of the osteology of Theco- 

 donlosannta and Paleeosaurtti; whose antiquity the disco- 

 verers of these genera regard as being greater than that 

 of any other vertebrated animals, excepting fishes : 



In their thecodont type of dentition, biconcave vertebrae, 

 double-jointed ribs, and proportionate size of the bones of 

 the extremities, they are nearly allied to the Telcosau- 

 rin; but they combine a lacertian form of tooth and 

 structure of the pectoral and probably pelvic arch with 

 these crocodilian characters, having distinctive modifica- 

 tions, as the moniliform spinal canal, in which however 

 the almost contemporary Rhynchosaur participates. 



Professor Owen adds that it would be interesting to 

 ascertain whether the caudal vertebrae are characterized, 

 as in the Thuringian Protosaur, by double diverging 

 spinous processes. 



Cladyodon, Owen. ' In the new red sandstone (keuper?) 

 of Warwick and Leamington,' says the Professor, ' there 

 occur ietached, pointed, trenchant, recurved teeth, the 

 crowns of which are sometimes 1 inch 4 lines in length, 

 and 5 lines across the base : they have been found in the 

 same quarries as those containing the remains of J.aln/ri'i- 

 thodon. In their compressed form, anterior and posterior 

 serrated edges, sharp points, and microscopic structure, 

 these teeth agree with those of the Saurian reptiles of the 



