412 MOLLUSCOIDEA phylum v 



Dalman (Fig. 623). Distinguished from Spirifer by having an 

 unusually high ventral area, with its narrow delthyrium closed by a perforated 

 pseudodeltidium, resulting from fused deltidial plates. 

 Silurian to Devonian ; Europe and North America. 



Siibfamily B, Reticüläriinae Waagen. 



Spiriferidae with a spinöse surface. Spiralia prdbahly 

 as in Triqonotretinae. Late Silurian to Permian. 



Cyrtia exporreda (Walil- 



Naturai size!"^^ ' ° ^"' " Beticularia M'Coy. Spirifers without alations, and 



generally without radial undulations. Surface with 

 imbricating lamellae that terminate in spines. Dental plates present. 

 Genotype B. reticulata M'Coy. Section Fimbriati {pars) Hall and Clarke. 

 Devonian to Lower Carboniferous ; widely distributed. 



Subgenus Prosserella Grabau. Small early Eeticulariae with well-developed 

 parallel and closely set dental lamellae. Late Silurian ; North America. 



Subgenus Sguamularia Gemmellaro. Like Beticularia^ but without dental 

 er septal plates. Carboniferous and Permian ; widely distributed. 



Siibfamily C. Martiniinae Waagen. 



Spiriferidae with a smooth surface. Spiralia prohally as in the Trigonotretinae. 

 Devonian to Permian. 



Amhocoelia Hall. Small, concave, or plano-convex, usually smooth Spirifer- 

 like Shells. Four well-defined adductor scars near the anterior margin in the 

 dorsal shell. Devonian to Carboniferous ; North America and Europe. 



Martinia M'Coy. Short-hinged Spirifers that in general have smooth or 

 concentrically marked exteriors, and rarely may be somewhat radially un- 

 dulate. No dental plates or median septa. Genotype Aiiomites glaher Martin. 

 Section Glahrati-Äseptati Hall and Clarke. Lower Carboniferous to Permian ; 

 distribution general. 



Subgenus Martiniopsis Waagen. Like Martinia, but with well-developed 

 diverging dental and septal plates. Permian ; India. 



Subgenus Mentzelia Quenstedt. Like Martinia, but with a prominent 

 ventral median septum. Triassic ; Europe. 



Metaplasia Hall and Clarke. Smooth Spirifer-\\kQ shells, with a median 

 fold on the ventral valve and a sinus on the dorsal valve. Lower Devonian ; 

 North America. 



Verneuilia Hall and Clarke. Small, smooth Spirifers, with a deep median 

 sinus and two pronounced angular divergent ridges on each valve. Devonian 

 to Carboniferous ; Europe. 



Family 4. Suessiidae Waagen. 



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

 Spiralia laterally directed. Jugum continuous and more or less V-shaped. 

 Shell structure highly punctate. Silurian to Jurassic. 



Cyrtina Davidson (Fig. 624). Cydm-like shells, with the dental lamellae 



