BRACHIOPODA. 103 



in palasozoic faunas in wliich tlie accessory lamellae attain so high a develop- 

 ment. As already observed, Bittner has detected a number of such 

 double-spired forms in the Alpine Trias, over all of which he extends the 

 generic term Athvris (or Spirigera), though he has introduced for them a 

 number of subordinate names based upon slight differences of structure, as 

 follows : 



Pexidella ; smooth forms with thickened shells, and loop of inconspicuous 



size. 

 DiPLOSPiRELLA ; smooth forms without shell-thickening and with prominent 



loop. 

 EuRACTiNELLA ; ciuctured forms with slightly developed area and broad ribs 



separated by deep, narrow furrows. 

 Anisactinella ; forms with alternating ribs, area and elevated deltidium. 



The duplication of the spirals has also been observed in other Triassic genera, 

 notably Koninckina, Suess, and Amphiclina, Laube ;* shells differing from 

 Kayseria and its Triassic allies in so many other points of structure that a close 

 phyletic connection between them seems highly improbable. 



Genus RETZIA, King. 1850. 



PLATE L. 



1845. Terebmiida, de Vernecil. Ball, ile la Soc. g-eol. de France, second sei-., vol. xi, p. 471, pi. xiv, 



figs. 10 ad. 

 18S0. Retz'm, King. Monogr. Permian Foss. England, p. 137. 

 1854. Retzia, Davidson. Inti'od. British Fossil Brachiopoda, p. S8, jil. vi, tig. 77. 

 1886. Retzia. (Ehlurt. Annates Sci. Geol., vol xix. No. 1, p. 24, pi. xi, tigs. 11 -19. 



" A Spiriferidia ; in general oval longitudinally ; ribbed or striated ; with 

 long punctures. Large valve foraminated at or near the apex of the umbone; 

 with a triangular area, and a closed fissure. Type Terebratula Adrieni, De Ver- 

 neuil." (King, Monogr. of the Permian Fossils of England, p. 137.) 



The term Retzia has come into general use as a designation for palaeozoic 

 brachiopods which have an elongate-ovate form and radially plicated exterior. 



*See Ladbb, Die Fauna der Schichten von St. Cassian, Zweit. Abtheil., p. 28. 1865. 

 Bbechbr, American Journal of Science, vol. xl, p. 211, pi. ii. 1890. 



