638 



MOLLUSCA 



PHYLÜM VI 



Family 12. Tropitidae Mojsisovics. 



Forms usualhj robust, hut ranging from compressed-discoidal to keg-shaped. Body- 

 chamher long. Surface usually highly ornamented with rihs and Jcnots. Septa are 

 goniatitic in some reversionary genera, ceratitic in the most primitive forms known, hut 

 mostly slightly digitate. There are no adventitious lohes, and not more than one 

 auxiliary lohe. 



The Tropitidae are derived from tlie gastrioceran branch of tlie Glypliioceratidae, 

 willi such forms as Protropites and Columhites as connecting links. 



Siibfamily A. Tropitinae Mojsisovics. 

 Similar to the Anarcestidae in the ephebic stage, but the young frequently ha^ 



volutions with highly trapezoidal sections. 

 section of a System of longitudinal 

 ridges and transverse costae. Sutures 

 have deep, narrow ventral lobes divided 

 by siphonal saddles with peculiar trun- 

 cated bases, which are often retained in 

 later stages. Sutures in ephebic stages 

 of some forms are similar to those of 

 Haloritinae ; the young have a more or 

 less prolonged coronate stage, and are 



Sliells higlily ornamented by the inter- 



www* 



Fig. 1204. 



Margarites jokelyi (Hauer). 

 Upper Trias ; Sandling, near 

 Aussee, Austria. 



Fio. 1205. 



Tropites .iihlmllaiHs (ILiuer). Upper Trias 

 AussiM', Auslvia. l/j. 



Fig. 1206. 



Discotropites sandlingensis (Hauer). Upper Trias 



California (after Hyatt and Smith). 



trJfTt'^ ^^^■. 'l°S' n-'^'"' '^^'^ ""' ^; 1149; 1205), Paratropües [Micro- 

 (ropites), BarrandeHe., Szih/lhtes Mojs.; Discotropite, H. and S. (Fig. 1206). Trias. 



