412 MOLLUSCOIDEA phylum v 



Cyrtia 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. 



Subfamily B. Reticdlariinae Waagen. 



Pio. 623. 



Spiriferidae with a spinose surface. Spiralia prohahly 

 as in Triqonotretinae. Late Silurian to Permian. 



Cyrtia exporrecta (Walil- 



Naturai size. ' ' Reticularia M'Coy. Spirifers without alations, and 



generally without radial undulations. Surface with 

 imbricating lamellae that terminate in spines. Dental plates present. 

 Genotype R. reticulata M'Coy. Section Fimhriati {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 Squamularia Gemmellaro. Like Eeticularia, but without dental 

 or septal plates. Carboniferous and Permian ; widely distributed. 



Subfamily C. Martiniixae Waagen. 



Spiriferidae with a smooth surface. Spiralia prohahly 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 Anomites glaber Martin. 

 Section Glabrati-Aseptati 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-Yike. 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 bases of the primary 

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

 Shell structure highly punctate. Silurian to Jurassic. 



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



