ttt SAURIA. 



teeth are in unequal number, the middle azygos tooth being longer 

 than the rest 



In Ckiroif* Professor Owen found the teeth slightly curved, simple, 

 and nearly equal, with the exception of the azygos intermaxillary tooth, 

 which is longer than the rest They are small at first, but increase as 

 they are placed backwards. [ClltROTES.] 



The typical Blind- Worms, or Anguians, have, according to the Pro- 

 fessor, only maxillary teeth ; the palatine teeth being absent In 

 Anguit f-^gtiu [BLIND- WORM] the first five of the upper teeth on 

 men aide are small, with cutting edges, and are placed on the inter- 

 maxillaries ; the next eight are much larger, pointed, and recurved, 

 and are separated by intervals. In general form therefore, Mr. Owen 

 observes, the teeth of the true Anyuit adhere to the Ophidian type ; 

 but in the Ophiomenu, or Miliary Blind- Worm, and in the Acontias, 

 they are conical, obtuse, and straight In the sub-genera Leritta, 

 Atilepkarui, flytleropiu, JHbamut, fyflilinui, and the rest of the family 

 of Blind- Worms, the teeth are likewise simple and conical. 



The Scincoidians, or Smooth-Scaled Lizards, have small mouths and 

 slender sharp teeth, fitted apparently, observes Professor Owen, for 

 insect food. [ScwciD*.] 



The teeth in Tropidopkorut are described as straight, cylindrical, 

 simple, slightly compressed at the summit, and confined to the jaws. 

 In the true Skiuks (.Seine**, Dum. et Bibr.), of which the .Scinciw 

 officinal** is the type, the palate also is furnished, four or five email 

 obtuse teeth being situated on each pterygoid bone. The maxillary 

 teeth of Scin&u are conical, obtuse, and sometimes slightly incurved. 



In the Chameleons, the same author states that the teeth are conical, 

 compressed, trenchant, with the summit simple, or terminating iu 

 three points, arranged in the same longitudinal line ; and that, in 

 most species, the teeth gradually increase in size, and become wider 

 apart as they are situated farther back upon the jaws. Professor 

 Owen further observes that the teeth are BO completely confluent with 

 the alveolar plate, as to appear, externally, when in place, to be mere 

 processes of that border of the jaw ; but, he remarks, their true 

 nature is evident when viewed from the inner side of the jaw. The 

 number of teeth vary in the species. [CHAMELEONS.] 



In the Agamanians, or Agamoid Lizards, forming the genus I'ro- 

 mattyx, the dentition, which at first sight seems to consist of a merely 

 notched or dentated margin of the jaw, resembles that of the Chame- 

 leons. These notches, or processes, are however true teeth, originally 

 developed as independent parts, and afterwards becoming confluent, 

 by their base and a great part of the outer side, with the alveolar 

 parapet of bone. 



The canines of the Dragons [DRACOXINA] are proportionally longer 

 than those of SteUio, but otherwise the dentition is the same. 



There is a resemblance between the mutable A games (Trapelw) and 

 the Stelliontt, inasmuch as the former have two conical teeth longer 

 than the rest, beginning the series in the lower jaw and superior 

 maxillary bones ; but the Ayamir have four small conical intermaxil- 

 lary teeth, without corresponding teeth below. Seventeen triangular 

 teeth were found to succeed the canines in the lower jaw, and fifteen 

 in the upper jaw, in Trapclut aler. Agama orbicularii resembles the 

 Trapeli in its dentition, with the exception that the molar teeth 

 behind the canines are more conical 



In the Oeckotians [QECKOTIDA] the teeth are more pointed, more 

 slender, more equable, and more numerous than in the preceding 

 group. The Professor remarks that the summit of the tooth is always 

 simple, and that the base is obliquely soldered to the internal surface 

 of an outer alveolar parapet The number of the teeth varies very 

 much in the different sub-genera; but none of the Gcckotida: have 

 teeth on the roof of the mouth. 



The Iguanians [IOUANIDA] are characterised, like the preceding 

 groups, by a short contractile tongue, slightly notched at its extremity, 

 but, as he remarks, they are distinguished for the most part by having 

 teeth on the pterygoid bone, and also by the complicated form of the 

 crown of the maxillary teeth in the typical genera, the specict ->f 

 which subsist chiefly on vegetable substances. In most of the family 

 the U-cth are set in a common shallow oblique alveolar groove, and 

 are soldered to excavations on the inner surface of the outer wall of 

 the groove. 



The following genera are enumerated by MM. Dumdril and Bibron 

 as showing the pleurodont type of detition, and as being also furnished 

 with pterygoid teeth, namely: Polychnu, i'rottrophui, Anolit, Cory- 

 Ikophana, Baiilitcui, Aplojmnotut, Amblyrhynrhiu, Iguana, Afetopo- 

 ctrot, Cyclurui, Jlrac/iylvphut, Leioiaurut, JJyptibata, Proctotrtta, 

 Ecpkymolct, Hcnoccrcut, and Oplitnu. But the following plcurodonts, 

 Ifyperanodon, Tropidoltiiit, 1'hrynotona, and CaUitaurut, have no 

 pterygoid teeth. 



In the genera Iitiunu, Calota, Lophyrui, Otocryptit, and Chlamy- 

 aoiaurut among the Acrodonts, the maxillary teeth may, Professor 

 Owen observes, be divided into anterior, laniary, and posterior teeth ; 

 and ho state* that no Iguanian lizard has teeth on the palatine bones. 

 " The most strictly vegetable-feeding reptiles," says the Professor, 

 "are the true /guana and the Amblyrhynchi ; yet the size of the 

 teeth, their mode of implantation, and the limited motions of the 

 jaws permit only an imperfect comminution of the food by these 

 instrument* ; and their summits are rather chipped off than ground 

 down by use. The appearance of abrasion is greatest iu the posterior 



SAUUIA. 7 



teeth ; especially in the lyunn cornuta, iu which the crowns of the 

 treth are thicker than in the Iguana tuberculata, and make a nearer 

 approach to the very remarkable form of tooth that characterises the 

 gigantic Iguanodon. [loDANODON.] 



Professor Owen describes the fang of the tooth of Hylecosaurus as 

 pub-cylindrical, sub-elongate, and smooth ; the crown as expanded, 

 compressed, slightly incurved, and with the narrow sides straight and 

 converging at a slightly acute angle to the apex. In all the teeth 

 which the Professor had seen, these sloping sides showed the effects 

 of attrition, the enamel being worn away and the dentine exposed. 

 The tooth is described as consisting of a body of dentine covered by 

 a thick coating of clear structureless enamel, and surrounding a small 

 central column of true bone, consisting of the ossified remains of the 

 pulp, which presents the usual characters of the texture of the bone 

 iu the higher reptiles. The dentine differs, like that of existing 

 Lacertians, from the dentine of the Jguanodon in the entire absence 

 of the numerous medullary canals which form so striking a charac- 

 teristic of the latter reptile. The main calcigerous tubes are described 

 as characterised by the slight degree of their primary inflections, and 

 as continued in an unusually direct course from the pulp-cavity to the 

 outer surface of the dentine at nearly right angles with that surface, 

 but slightly inclined towards the expanded summit of the tooth. 

 They are stated to be chiefly remarkable for the large relative size of 

 their secondary branches, which diverge from the trunks in irregular 

 and broken curves, the concavity being always turned to the pulp- 

 cavity. In most ports of the tooth the Professor found the numbers 

 of these branches obscuring even the thinnest sections. The ossified 

 pulp exhibited the parallel concentric layers of the ossified matter 

 surrounding slender medullary canals, interspersed with irregular, 

 elliptical, radiated cells. [HYL.TOSAURCS.] 



Professor Owen observes that one gigantic extinct species of Saurian 

 Reptile [MOSASAURCS] has been found to agree with many of the 

 existing species in the Lacertian, Iguanian, Anolian, and Scincoid 

 families, in having the pterygoid bones armed with teeth ; but, he 

 remarks, the maxillary teeth combine the pleodont with the acrodont 

 characters; and the skeleton indicates a special adaptation for swim- 

 ming and marine life. 



The teeth of Geoiaurui, which appears not to be happily named, 

 inasmuch as the large eyes defended by broad sclerotic plates indicate, 

 as Professor Owen observes, that the sea was its dwelling-place, 

 resemble those of the large Varanians in their compressed subrecurvcd 

 crown, with a trenchant anterior and posterior edge, which likewise 

 presents a fine and close dentition. A very fine fragment, we believe, 

 the best known, is in the British Museum. Sommering's conjecture 

 that Gcosatiruus might be a young Mosasaur U no longer held good, 

 and Cuvier's observations on the difference of their teeth are acknow- 

 ledged to be just Professor Owen remarks that the form of the 

 vertebrae of (je.oiav.ru3 indicates its near affinity to the crocodilian 

 group, and that the Argeuton fossil crocodile presents the same 

 subcompressed teeth with dentated margins as Geosauria. 



The Varanians form a family of tcaled Sauriaus, including the 

 Monitors of the Old World : some of the species come nearest in size 

 to the crocodiles. This family, Professor Owen remarks, manifests 

 its affinity to that group in the absence of pterygoid teeth, and in the 

 number of successive tooth-germs which may be observe I at the 

 same time behind the fixed and functional teeth. Independently of 

 these characters, the Varanians must excite our interest from exhibit- 

 ing in some species a form of tooth which most nearly resembles that 

 which characterises Mryakuaurus and other very remarkable extinct 

 terrestrial species of gigantic squamate Saurians. 



In a small extinct species of Lizard from the gault and chalk 

 formations, and for which Professor Owen proposes the name of Rapltio- 

 taurut, the teeth are awl-shaped, about three lines in length above 

 the alveolar border, close-set, and equal-sized. Their rounded base 

 was anchylosed to the alveolar groove, and their outer side attached 

 to a well-developed external alveolar wall. 



For the varieties iu the form of the teeth presented by the existing 

 Varauians we must refer to the work itself, observing only that 

 Professor Owen points out the Ihlodtrm, Varanui Niloticut, V. 

 arenariui, V. Timoricntii, V, Jiengalentu, V. bivittatui, V. varugatui, and 

 V. crocodilinui as the principal species which exhibit such varieties. 



Professor Owen commences the family of the Thecodonts, extinct 

 Saurians which exhibit a mode of fixation of the teeth different from 

 the Acrodouts and Plcurodonts, with the genus T/iccodonlotaunit, 

 observing that these Thecodoute, which in other parts of their organi- 

 sation adhere to the squamate or Lacertine division of the order, have 

 their teeth implanted iu sockets, either loosely, or confluent with the 

 bony walls of the cavity ; and to this group the most ancient Saurians 

 belong. 



The Thecodonloiaurui discovered by Dr. Riley and Mr. Stutchbury 

 in the Dolomitic Conglomerate at Itedland near Bristol, is, as well as 

 their Paltcosaurtu, also there found by them, allied in the form of the 

 teeth to the typical Varanian Monitors, but they differ in having the 

 teeth imbedded in distinct sockets : to this condition however the 

 Varani make an approach in the shallow cavities containing the base 

 of the teeth along the bottom of the alveolar groove. 



One of the two teeth of Palaioiaurui found by Dr. Riley ami Mr. 

 Stutchbury is compressed and pointed, with opposite trenchant and 



