528 



MOLLtTSCA 



SUB-KINGDOM VI 



Family 3. Actinocaratidae. 



Orthoceracones and cyrtoceracones with siphuncle more or less filled by rings of 

 organic deposits, and having an endosiphunde in the central axis. Camerae m,n/ i><> 



empty or filled to various degrees with organic 

 deposits, even to the extent of solidifying the entire 

 shell previous to gerontic stage. Shells smooth or 

 annulated, but not longitudinally ridged, at least in 

 the later stages. 



Actinoceras, Bronn. (Figs. 1077, 1078). Ortlm- 

 ceracones and cyrtocera- 

 conesof usually depress, v [ 

 elliptical section, with 

 large, excessively num- 

 muloidal siphuncle. 

 Funnels very short and 

 crumpled, sheath almost 

 globular. Internal de- 

 posits contracting the 

 central axis into an 



Artlnocems vertebratum, Hall. 

 Actinoceras cochleatum, Schloth. Silurian ; Lockport, New York, annulated eiKlOSlphimcle 

 Silurian; Gottland. Abraded fragment Longitudinal section showing witTi fnl-mli v-i/Iio+ii-. 

 showing single septa and thick, annulated organic deposits of siphuncle 

 endosiphuncle. 1/2- (after Barrande). . from the annuli. Septa 



often double, with an 



interspace between the two layers near the siphuncle, but solid near the shell. 



Ordovician to Carbon- 

 iferous. 



Sub-genera : Ormocerux, 

 Stokes (Fig. 1079). Ordo- 

 vician to Carboniferous. 

 Paractinoceras, sub - gen. 

 nov. (Fig. 1080). Shells 

 longer and more slender 



FIG. 1079. 



Actinoceras (Ormoceras) Bayfieldi, 

 Stokes. Ordovician ; Lake Huron, 

 Canada. Longitudinal section showing 

 organic deposits of siphuncle partly 

 dissolved away (after Stokes). 



FIG.' 1080. 



Actinoceras (Paractinoceras) 

 docens, Barr. sp. Silurian 

 (E) ; Dvoretz, Bohemia. Ver- 

 tical section showing senile 

 stage without organic de- 

 posits, preceded by adult 

 stage with siphuncular 

 rosettes (after Barraude). 



FIG. 1081. 



Huronia vertebralis, 

 stokes. Ordovician ; Isle 

 Drnnimond, Lake Huron. 



Siphuncle. 



than in the preceding, with large siphuncular segments confined to early stages, and 

 very long living chamber. Type P. (Sact.) canadense, Whiteaves sp. Silurian. 



Cyrtactinoceras, gen. nov. Type C. (Cyrt.) rebelle, Barr. sp. Deiroceras, Hyatt ; 

 Huronia, Stokes (Fig. 1081) ; Discosorus, Gonioceras, Hall. Silurian. 



