SUB-ORDER t) ORTHOCHOANITES 523 



Family 13. Bhadinoceratidae. 



Primitive discoidal gyroceracones and nautilicones with stout ml <;,,,, .. ,-:,-< n I, ,,- >.: 

 <!' l>ressed elliptical in section, but becoming reniform in later >/-/</> ./' nmitilir 

 Shells with longitudinal ridges and sometimes annular folds in tl /////M/, /,/// ,,ff. n 

 smooth in ephebic stage. Sutures with ventral, lateral, and dor ant //*-., /,/ almost 

 straight. Siphuncle nummuloidal and often dorsad of centre. Annular lobes known to 

 be present in specialised forms. 



Bhadinoceras, Nephriticeras, Hyatt. Devonian. 



Family 14. Trigonoceratidae. 



Gyroceracones and nautilicones having at some stage or ////<///, //,/'/ life trigonal 

 volutions, a more or less concave venter, and generally fluted shell. Sutures with ventral 

 saddles in the young, becoming divided by shallow lobes in later stages, and in some genera 

 the dorsal lobes of the young become divided subsequently by dorsal saddles. Gerontic 

 living chamber occasionally free near the aperture. Annular lobes observed in only one 

 species (Apheleceras disciforme). Young have longitudinal ridges roii<ih>-ni<I bij transverse 

 bands as in Thoracoceras. Siphuncle small, ventrad of centre. 



Trigonoceras, M'Coy ; Coelonautilus, Foord (Trematodiscus, Meek ; Trematoceraa, 

 Hyatt) ; Subclymenia, d'Orb. ; Stroboceras, 

 Apheleceras, Diorugoceras, Ephippioceras, 

 Hyatt. Carboniferous. All nautilicones 

 but the first, which is gyroceraconic. 



Family 15. Triboloceratidae. 



Gyroceracones and nautilicones similar 

 to Trigonoceratidae, and with concave 

 venter at an early stage or until late in 

 life. The venter afterwards becomes more 



or less elevated, and in most species convex. Fio. 10:0. 



Sutures also similar, but annular lobes VestinauMus Koniwki, <l'0rb. 81 ,. Carboniferous 

 nrp <nrt><ipnt in nil t~hp 'nfit/tiJirn'nfl<i <tniip Limestone; Tournay, Belgium. < >ral and lateral 



are presen in all we nautilicones save aspects of y ' oung indl ft dua i t With umi.iiical perforation. 

 Coloceras. 



Triboloceras, Hyatt ; Vestinautilus, Ryckh. (Fig. 1070) ; Planetoceras, Stearoceras, 

 Coloceras, Hyatt. Carboniferous. 



Family 16. Rhlneceratidae. 



Gyroceracones and nautilicones like Thoracoceras in nepionic stage, but subsequently 

 becoming biangular in section, and generally developing solid, more or less tetragonal 

 volutions. Longitudinal ridges and flutes also developed, but more uniform in size than 

 in the preceding family, and venter always convex. Annular lubes present in all 

 nautilicones so far as known. 



Bhineceras, Lispoceras, Thrincoceras, Phloioceras, Discitoceras (Discites, M'Coy), 

 Leuroceras, Phacoceras, Hyatt. Carboniferous. 



VI. HERCOCERATIDA. 



Primitive shells have projecting bands of growth and processes similar to those of 

 primitive Ryticeratida, but less numerous, being present in only one row, and evolving 



