CLÄSS II 



BRACHIOPODA 



391 



Proboscidella (Ehlert. Valves very unequal; dorsal valve small, concave, 

 operculiform ; ventral valve larger, convex, furnished with two lateral expan- 

 sions which bend downward to meet the margins of the dorsal valve, and an 

 anterior expansion, which is produced forward into one, or occasionally two, 

 long cylindrical tubes. Carboniferous ; Europe and North America. 



Subfamily C. Strophalosiinae, noviim. 

 Produdids anchored to foreign objeds hy the spines or hy most of the ventral shell. 



Chonopedus Hall and Clarke. Chonetes-like shells, but cemented ventrally 

 to extraneous objects. External surface reticulated by a double, oblique 

 series of concentric lines and fine radiating Striae. Lower Carboniferous ; 

 North America. 



Strophalosia King (Orthothrix Geinitz ; Leptaenalosia King) (Fig. 581). 

 Shell productoid in general 



form, cemented by the ven- 

 tral umbo. Both valves 

 with well-defined area, del- 

 tidium and chilidium. Ven- 

 tral valve with two pro- 

 minent teeth unsupported 

 by dental plates. Muscular 

 impressions small ; brachial 

 ridges distinct. Surface of 

 ventral valve covered with 

 spines ; that of the dorsal 



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Fig. 581. 

 Strophalosia goldfussi (Münst.). Permian ; Gera, Germany. A, 

 Dorsal aspect. B, Profile. C, Interior of dorsal valve with brachial 

 impressions. Natural size. 



Middle Devonian to Permian ; 



valve either spinous, lamellose or smooth. 



Europe, India, North and South America. 



Aulosteges Helmersen. Much like Strophalosia, but not cemented by the 



ventral umbo ; deltidium covered with small spinules and the surface of both 



valves thickly set with spines. Permian ; Russia and India. 



Etheridgina (Ehlert. Shell very small, nearly as broad as long, and 



attached to foreign bodies, notably crinoid stems, by the spines of the ventral 

 valve. Dorsal valve with a small beak ; surface ornamented 

 by concentric flexuous plications bearing a few scattered 

 spines. Carboniferous ; Scotland. 



Family 4 Richthofeniidae Waagen. 



Strophomenacea developed out of the Produdidae, and 

 remarkably modified by ventral cementation. The form is that 

 of cyathophylloid corals with an operculiform dorsal valve. 

 Shell strudure cystose. Upper Carboniferous and Permian. 



Tegulifera Schellwien. A youthful expression of the 

 highly modified Eichthofenia, in which the productoid 

 characters are still recognisable. Upper Carboniferous; 

 Au Stria. 



Eichthofenia Kayser (Fig. 582). These most remarkably 



Fio. 582. 



Richthofenia lawrenci- 

 a«a Waagen. Permo-Car- 

 boniferons ; Salt Range. 

 Vertical section of ven- 

 tral valve (after Waagen). 



