CLASS II 



BRACHIOPODA 



419 



Subfamily C. Koninckininae Waageii. 



Highly specialised Athyridae with jugmn and spiralia essentially as in Diplo- 

 spirellinae. The spiralia, however, are not laterally directed as in the former group, 

 but point ventrally, this being due to the concave form of the dorsal valve. Triassic 

 and Jurassic. 



Koninchina Suess (Fig. 634). Shell sub-orbicular, concavo-convex, smooth, 

 with a straight hinge-line, or strophomenoid in external appearance. Car- 

 dinal area obsolete at maturity. The accessory spirals take their origin 



Fio. 634. 



Konincldna leonhardi (Wis.sm.). Upper 

 Trias ; St. Cassian, Tyrol. A, Shell show- 

 ing spiralia, enlarged. B, Ventral and 

 dorsal aspects, i/j. , 



Fig. 635. 



Amphicliwi, with re- 

 stored brachidia (after 

 Bittner). 



Fic. 636. 



Thecospira haidingeri (Suess). 

 Rhaetic ; Starhemberg, Austria. 

 A, Ventral valve, i/i. B, C, 

 Brachidia, enlarged (after Zug- 

 meyer). 



from the upper surface of the jugum, and are coextensive with the primary 

 spirals. Trias ; Europe. 



Amphiclina Laube (Fig. 635). Like Koninckina, but sub-trigonal in out- 

 line, and with well-developed cardinal area and deltidial plates. Trias and 

 Jura ; Europe. 



Koninckella Munier-Chalmas. Similar to Amphiclina, but with well- 

 developed cardinal process. Trias and Jura ; Europe. 



Amphiclinodonta Bittner. Like Amphiclina, but with interlocking denti- 

 culate ridges and tubercles within the margins of the valves. Alpine Trias. 



Koninckodonta Bittner. Like Koninckina, but with prominent cardinal 

 areas and a row of sub-marginal thickened tubercles on the interior of the 

 ventral valve, which interlock with similar callosities on the dorsal valve. 

 Alpine Trias. 



Thecospira Zugmeyer (Fig. 636). Ventrally cemented Koninckininae with 

 well-developed cardinal area and cardinal process. Alpine Trias. 



Range and Distribution of the Brachiopoda. 



Owing to their great abundance, world-wide distribution and remote 

 antiquity, as well as their excellent state of preservation, Brachiopods occupy 

 a very conspicuous rank among extinct Invertebrates, and furnish us besides 

 with a large number of important stratigraphic index fossils. The composi- 

 tion of their shells, usually of calcite, enables them to resist the destructive 

 action of the fossilisation process more successfully than the shells of Mollusks, 

 many of which are composed wholly or in part of aragonite. Their value 

 as index fossils, however, is somewhat lessened owing to the difficulty of 

 identifying numerous genera, without a knowledge of their internal structure, 

 and this is often difficult to ascertain. 



