Palceozoic Bivalved Entomostraca. 61 



Tlie foreo'oing have a smooth surface, as is usual with this 

 genus ; whereas the specimen under notice has a minutely 

 reticulate ornament. Tt occurs with Primitia hevigafa (fig. 3) 

 in a micaceous and calcareous sliale, thin, hard, brittle, and 

 brownish, from the Arpatschai Valley in Armenia; collected 

 by Ur. G. Sievens during a journey in the Caucasus (see 

 Dr. Fr. v. Sandberger's note in the ' Neues Jahrb. f. Min.,' 

 &c., 1873, p. 58), where these and probably other species are 

 associated with Sjnnfer caharatas, J. Sow. (^= Sp. Verneuili^ 

 Murchison), and Rliynchonella cuhoides. 



The reticulation much resembles that of Bytliocyprisl 

 favulosa^ Jones, Americ. Geol., December 1889, p. 3o8, 

 tigs. 1 and 2. The latter is figured with its convex border 

 upwards, and is more oblique and much narrower. 



2. Primitia mioidula, Jones, var. sacculus, nov. 

 Sandberger, MS. (PI. VII. fig. 7.) 



Leiio-th. Height, 



ruillim. milliin. 



•8 -5 



Beyrichia mundula, Jones, Ann. & Mag. Nat. Ilist. ser. 2, vol. xvi. 

 1855, pp.90 and 174, pi. v. %. 23, and pi. vi. tig. 26 {"simplex, 

 var."), and figs. 28-31. 



Primitia mundula, Jones and Holl, ibid. ser. 3, vol. xvi. 1865, p. 419. 



Primitia mundula, Jones, Proceed. Geol. Assoc, "Pateoz. Biv. Entoni.," 

 1869, pp. 8, 10, and 13, figs. i. and ii. 



Primitia mundula, Jnues, Ann. & Mag. Nat. Hist. ser. 6, vol. iii. 1869, 

 pp. 375 and 378, pi. xvi. tigs. 1 and 2, 4-9, pi. xvii. tig. 1, and wood- 

 cut, fig. 2, p. 376. 



Primitia mundula, Jones, Americ. Geologist, December 1889, p. 337. 



Primitia mundula, var., Jones, Quart. Journ. Geol. Soc. vol. xlvi. 



1890, p. 5, pi. iv. tig. 7. 



Primitia mundula and varieties, Jones, Contrib. Canad. Micropalfeont., 



Part III., 1891, p. 64, pi. x. tigs. 8 and 9, and p. 72. 

 Primitia mundula, Krause, Zeitsch. Deutsch. geul. Gesell. vol. xliii. 



1891, p. 495, pi. XXX. tigs. 5-7. 



Primitia mundula and varieties, Jones, Quart. Journ. Geol. Soc. 

 vol. xlix. 1893, pp. 291 and 299, pi. xii. figs. 2-6, and pi. xiii. 

 figs. 11-15. 



This hollow cast of the right-hand valve of Primitia is 

 rather more oval than the typical form (see Ann. & Mag. Nat. 

 Hist. ser. 6, vol. iii. p. 376, woodcut, fig. 2, and pi. xvi. 

 fig. 9). Among the many varieties that have been noticed, 

 modifications in the outline of the valves and in the dimen- 

 sions of the sulcus are frequent. In this instance the sub- 

 oblong valve (its edges seem to be fully represented in the 

 intaglio cast) has the ends not quite equal in curvature, but 

 more so than in the type-form ; and the sulcus stretches 



