336 MOLLUSCOIDEA—BRACHIOPODA SUB-KINGDOM V 
The species of Spirifer have recently been grouped by Hall and Clarke into six 
sections as follows :—Radiati, with fine filiform striae; Lamellosi, with concentric 

. + Fic. 576. 
A, Spirifer striatus, Sow. Carboniferous Limestone; Ireland. Portion of dorsal valve removed, showing 
spiralia, 3/4 (after Davidson). , S. speciosus, Schloth. sp. Devonian; Eifel. 1/). C, S. macropterus, Goldf. sp. 
Devonian; Coblenz. Cast, 1/4. D, S. Mosquensis, Vern. Sub-Carboniferous; Moscow. £, Same, interior of 
ventral valve, 1/; (p, Pseudodeltidium ; z, Dental plates). 
lamellae (= Delthyris, Dalman) ; Fimbriati, with concentric rows of fine spines (= Reti- 
cularia, M‘Coy); Aperturati, with plications on fold and sinus ; Ostiolati, with the 
median fold and sinus without plications; Glabrati, with the surface smooth and 
glabrous (= Martinia, M‘Coy ; Martiniopsis, Waagen ; and Mentzelia, Quenstedt). 
Cyrtia, Dalman (Fig. 577). Distinguished from Spirifer by having an 
unusually high ventral area, with its delthyrium closed by a perforated 
deltarium. Silurian to Devonian; Europe and North 
America. 
Syringothyris, Winchell. Spirifer-like shells, usually 
with large and erect cardinal areas and an internal tube 
or syrinx, situated in the delthyrium. Carboniferous ; 
North America and Europe. 

Fic. 577. 
Cyrtia exporrecta, Dalm. Ambocoelia, Hall. Small, concave, or plano-convex, 
Silurian ; Gotland. Natural ysyally smooth Spirifer-like shells. Four well-defined 
size. 
adductor scars near the anterior margin in the dorsal 
shell. Devonian to Carboniferous ; North America and Europe. 
Vernewilia, Hall and Clarke. Small Spirifers, with a deep median sinus 
and two pronounced divergent ridges on each valve. Devonian to Carboni- 
ferous ; Europe. 
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