ZOOLOGY. dSd 



six genera, Lave beeu discovered. Tliese Lave been named and iiidi. 

 cated in tLe American Journal of Science, as follows : 

 XV. 1878, June (459). Dryolestes priscus. 



xviii. 1879, July (Gl). Stylacodon gracilis. (Styloduutida^ named.) 

 xviii. 1879, Sept. (215). Dryolestes vorax. 



(210). Tinodon bellus) (Tinodoutidaj named.) 

 xviii. 1879, jSTov. (390). Ctenacodou serratus. (Plagiaulacidte t^Gill 



1871) renamed.) 



(397). Dryolestes arcuatus. (Dryolestidte named.) 



(397). Tinodon robustus. 



(398). Tinodon lepidus. 

 XX. 1880, Sept. (235). Diplocynodon Aictor. 



(230). Stylacodon validus. 



(230). Tinodon ferox. 



(237). Triconodon bisulcus. 



(237). Dryolestes obtusus. 



In a very recent contribution to tLe knowledge of tLese types, Pro- 

 fessor MarsL Las proposed to differentiate certain of tLese forms into 

 two orders, one of wLicL Le nas named Fantotheria and tLe otLer AUo- 

 tlieria.* 



TLe Fantotheria are distinguisLed by "(1) cerebral LemispLeres 

 smootL ; (2) teetL exceeding or equaling tLe normal number, 41 ; (3) 

 liremolars and molars imperfectly differentiated ; (4) canine teetL witL 

 bifid or grooved fangs; (5) rami of lower jaw unancliylosed at sympLysis; 

 (0) myloLyoid groove distinct on inside of lower jaws ; (7) angle of lower 

 jaw witLoiit distinct inflection; (8) condyle of lower jaw near or below 

 Lorizon of teetL ; and (9) condyle vertical or round— not transverse." 

 To tLe group tLus defined Professor MarsL tLiuks tLat, witL tlie ex- 

 ception of a very few aberrant forms, tLe known Mesozoic mammals 

 may be mostly referred. 



Th.Q Allotheria are distinguisLed by Laving "(1) teetL mucL below tLe 

 normal number; (2) canine teetL wanting; (3) i^remolar and molar 

 teetL specialized; (4) angle of lower jaw distinctly inflected; (5) 

 myloLyoid groove wanting." TLe group so distinguisLed is xirojiosed for 

 tLe genus Flagiaulax, represented by a species originally described 

 by Owen, and of wLicL representatives Lave been likewise found in 

 America, and to it are referred tLe new genus Ctenacodon of MarsL, 

 " and possibly one or two otLer genera." 



It will be out of place to traverse tLe conclusions of Professor MarsL, 

 but tLose best acquainted witL tLe mammals will agree tLat wLatever 

 may be tLe relations of tLe forms above diflerentiated, it still remains 

 to be proved tLat tLey are entitled to ordinal distinction, for certainly 

 tLe cLaracters adduced are not generally considered to be entitled to 

 sucL value by tLe majority of modern tLerologists. 



'Marsh (O. C). Notice of Jurassic Mammals represeutiug two new Orders. Am. 

 Journ. Science, (3,) vol. xx, \}]}. 235-239, Sept. 1880. (See, also, vol. xv, p. 459; vol. 

 xviii, pp, 60, 215, 396, 1879.) 



