410 MOLLUSCOIDEA phylüm v 



Family 2. Oyclospiridae, noviim. 



Primitive Spiriferacea with the crura directly continuous with the hases of the 

 primary lamellae, which are closely set and nearhj parallel. Spiralia very dightly 

 introverted and of hut three or less volutions ; no jugum present. Middle Ordovician. 



Cyclospira Hall and Clarke. Small, smooth, rostrate shells, with a deep 

 ventral and a shallow dorsal valve. Dorsal hinge-plate supported by a median 

 septum. Middle Ordovician ; North America. 



Family 3. Spiriferidae King. 



Derived Spiriferacea with the crura directly continuous with' the hases of the 

 primary lamellae, which are situated hetween the laterally directed spiralia. Jugum 

 simple, complete, or incomplete. Silurian to Jurassic. 



Subfamily A. Spiriferinae, novum. 



Spiriferidae with the jugum discontinuoiis at maturity, represented by two short 

 jugal processes, one attached to each primary lamella. Shell structure with scattering 

 perforations, hut never regularly punctate. Silurian to Permian. 



Spirif er Bowerhy. This name has been made to cover a vast number of 

 Paleozoic Brachiopods having a more or less alate form, a multiplicate surface, 

 and terminally directed spiralia. Yarious attempts have been made to group 

 the species into phyletic series, but as there is present more or less of homoeo- 

 morphic development a completely satisfactory arrangement is not yet at 

 band. The following scheme is of tentative character. 



Spirifer Sowerby sensu stricto {Fusella M'Coy) (Fig. 622, A). Transverse, 

 usually alate Spirifers with the entire shells more or less closely plicate ; 

 plications simple or dichotomous. Short dental plates developed, but no high 

 median septa in either valve. Genotype Anomites striatus Martin. Section 

 Aperturati Hall and Clarke. Devonian to Permian ; distribution general. 



Section Spiriferella Tschernyschew. , A group of subquadrate Spirifers 

 suggesting S. cameratus, but with the surface finely papillose. Ventral shells 

 very thick, with strong dental plates. Upper Carboniferous ; Urals, Alaska 

 and North America. 



Section Trigonotreta Koenig. Early, coarsely plicate Spirifers in which 

 the plications are simple and not dichotomous. Genotype S. aperturatus 

 Schlotheim. Devonian ; Europe and America. 



Section Choristites Fischer (Fig. 622, D). Quadrate Spirifers that are 

 decidedly multiplicate and have long dental plates. Genotype S. mosquensis 

 Vern. Carboniferous ; Europe and America. 



Section Dzieduszychia Siemiradz. Large short-hinged Spirifers with a 

 plicate sinus in either valve. Genotype Terehr. hielcensis Roemer. Middle 

 Devonian; Europe. 



Section Brachythyris M'Coy. Rounded, tumid, short-hinged Spirifers, with 

 broad and depressed plications tending to be absent on fold and sinus. 

 Genotype S. ovalis Phillips. Carboniferous ; Europe and America. 



Subgenus Adolfia Gürich (Fig. 622, B, G). Quadrate to alate, multiplicate 

 but not dichotomously plicate Spirifers, that have no plications on fold or 

 sinus ' (rarely, the fold is bilobed and then there may be a plication in the 

 sinus). Surface pustulose or finely pustulo-striate. Dental plates short ; no 

 ventral median septum. Genotype aS^. deflexus Roemer. Section Ostiolati 



