418 MOLLUSCOIDEA phylum v 



Actinoconchus M'Coy. Athyrids with very wide, radially striate, concentric 

 lamellae. Carboniferous ; Europe. 



Cleiothyridina Buckmaii (Cleiothyris King, non Phillips). Athyrids with con- 

 centric rows of flat spinules. Carboniferous and Permian ; distribution 

 general. 



Composita Bronn (Seminula Hall and Clarke, non M'Coy). Genotype Spirifer 

 amhiguus Sowerby. Smooth-shelled Athyrids. Dorsal hinge-plate very pro- 

 minent. Carboniferous ; distribution general. 



Comelicania Frech. Large, decidedly alate Athyrids with arigulated sinuses 

 in both valves. Alpine Upper Permian. 



Janiceps Frech. Small, sharply triangulär Athyrids with angulated sinuses 

 in both valves. Alpine Upper Permian. 



Spirigerella Waagen. Permian ; South America and India. 



Amphitomella Bittner. Smoot'h - shelied 

 Athyrids with a double cardinal process and 

 median septa in each valve. Alpine Trias. 



Tetraäinella Bittner (Plicigera Bittner) 

 (Fig. 633). Athyrids with four correspond- 

 ing ribs on each valve. Alpine Trias. Sub- 

 genus : Stolzenhurgiella Bittner. Alpine Trias. 

 ^ , . „ .„.„,,,. X Pentadinella Bittner. Athyrids with five 



Tetractmella tmgoiulla (ßc\\\ot\\Gim). ,. ., , ~ ^ 



Muschelkalk; Recoaro, italy.. i/i- corrcspoudmg ribs on each valvc. Uccurs in 



the Alpine Trias. 

 Anomactinella Bittner. Athyrids with a number of angular alternating 

 ribs towards the anterior margins. Alpine Trias. 



Pomatospirella Bittner. Small smooth shells having the contour of Dayia 

 or Cyclospira. Alpine Trias. 



Subfamily B. Diplospirellinae Schuchert. 



Specialised Athyridae {out of the Athyrinae), with the jugal bifurcations very 

 long, lying hetween the volutions of the spiralia, and continuing with these to their 

 outer ends. Sometimes there is an additional jugal process which articulates with the 

 ventral valve, or recurves and joins the jugum. Devonian to Triassic. 



Kayseria Davidson. Lenticular, plicated shells with a median plicated 

 sinus on both valves. Jugum with a ventral articulating process and the 

 bifurcations continued between the spiral ribbons to their outer ends. 

 Devonian ; Germany. * 



Diplospirella Bittner. Athyrids with the jugal processes coextensive 

 with the principal spiral coils. Alpine Trias. 



Pexidella Bittner. Athyrids difFering from Diplospirella in that the 

 jugum is much reduced and situatedj^in the umbonal region. Valves much 

 thickened in the apical region. Alpine Trias. 



Euractinella Bittner. Diplospirellids with short corresponding ribs. 

 Alpine Trias. Didymospira. Salomon. Alpine Trias. 



Anisactinella Bittner. Diplospirellids with alternating ribs, The 

 secondary spiral coils give off a process which returns and joins the jugum. 

 Alpine Trias. 



