410 MOLLUSCOIDEA phylum v 



Family 2. Oyclospiridae, novum. 



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

 primary lamellae, which are closely set and nearly parallel. Spiralia very slightly 

 introverted and of but 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 directUj continuous with the bases of the 

 primary lamellae, which are situcded between the laterally directed spiralia. Jugum 

 simple, complete, or incomplete. Silurian to Jurassic. 



Subfamily A. Spiriferinae, novum. 



Sjjiriferidae with the jugum discontinuous at maturity, represented by two short 

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

 perforations, but never regularly punctate. Silurian to Permian. 



Spirifer Sowerby. 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. Various 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 

 hand. The following scheme is of tentative character. 



Spirifer Sowerby sensn sfricto {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. Genot3'-pe 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 Terebr. kielcensis Roemer. Middle 

 Devonian ; Europe. 



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

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

 Genotype *S^. ovcdis Phillips. Carboniferous ; Europe and America. 



Subgenus Adoljia Giirich (Fig. 622, ^, C). 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 S. deflexus Roemer. Section Ostiolati 



