56 Prof. T. Rupert Jones — Fossil Estherm. 



The other species shows very numerous riblets, thickly set, more 

 particularly towards the front and ventral borders ; these are less 

 sharp, and almost equal in breadth with the spaces between them. 

 In particularly well-preserved specimens about 30 were counted, in 

 others 20; but the number is difficult to determine; and we must 

 recognize the difference of the two forms in the above-mentioned 

 characters. This second species is evidently the Wengensis of Giebel. 

 Note at p. 711. — Dr. E. Weiss named the first of the two foregoing 

 species Estheriella lineata, and the latter JS. costata; but he had a 

 doubt about the naming, and thought that these names should be 

 withdrawn until perfect proof of the difference between his and 

 Giebel's species should be arrived at. 



Dr. E. Weiss, though inclined to look on these two forms as 

 belonging to a new genus, thought that it might suffice, with their 

 great resemblance in general habit to Estheria, to place the radially- 

 ribbed shells of Diirrenberg as a subgenus only, with the name 

 Estheriella. 



For the form with about 12 ledge-like riblets (E. lineata, Weiss, 

 the nodocostata of Giebel), he gives — 



mm. Proportion. 



The height to the breadth (length) = 2-8 : 4-3 = 1:1-5 



3-2 : 4-3 = 1 : 1-3 

 ,, „ „ 2-7 : 3-5 = 1 : 1-3 



For the form with over 20 riblets and furrows (E, costata, Weiss, 

 the Wengensis of Giebel), — 



mm. Proportion. 



Near Diirrenberg there are other horizons of Estheria. In the 

 boring they are found at a depth of about 200 metres ; near the 

 Eoyal Saltworks were found some very small Estherioe (without 

 riblets'), also on the left bank of the Saale, some feet below the 

 first coarse white sandstones of the Middle Buntersandstein, at the 

 cliff between Graslau and Leina, near Corbeth. 



Note. — E. nodocostata (Giebel) retains its name, the form being 

 recognized as that which Giebel figured and described in 1857. His 

 Wengensis, however, is not the Fosidonomya so named by Wissmann; 

 nor is it from Wengen ; and the name proposed by Weiss, namely, 

 costata (though too near to nodocostata for convenience), should take 

 its place. 



In the " Memoires du Comite Geologique," 4to. St. Petersburg, 

 vol. vi. 1888, P. Kratow describes and figures two small bivalves 

 with radial stride as EstJieriella trapezoidalis, pp. 469 and 657, pi. ii. 

 fig. 27, and E. oblonga, pp. 470 and 557, pi. ii. fig. 28 (reaching 



^ Fig. 12 of PI. II. may be one of these small Estherice, possibly E. Germari, 

 Beyrich. 



