116 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 



13. Anthracomta minima, Ludwig. Plate XVI, figs. 21, 22, 24 — 34. 



? Modiola minuta, Brown. Fossil Conch., 1819, pi. lxxii, fig. 29. 

 Non — minima, Brown. Ibid., pi. lxxii, fig. 28. 



Anodonta minima, Ludwig. Palaiontographica, Bd. viii, 1859-60, p. 36, pi. v, 



fig. 14. 

 Modiola Caelotta, Burner. Geol. und Palseontol. von Oberschlesieu, 1870, 



p. 76, foot-note. 



— sp., Volpersdorf. Zeitschrift der Deutsch. Geol., vol. xvii, 1865, p. 276, 



Taf. vi, fig. 6. 



— (or Anthracomta), undescribed form, Salter. ' Iron Ores of South 



Wales,' Geol. Surv. Mem., 1861, p. 233, 

 pi. ii, figs. 1, 2. 

 Anthracomya minima, Hind. Quart. Journ. Geol. Soc, vol. xlix, 1893, p. 272, 



pi. ix, figs. 11, 12. 



Specific Characters. — Shell small, ovately and obliquely triangular. The 

 anterior end is very short and tumid, with a rounded border. The posterior part 

 forms the greater portion of the shell ; it is expanded and compressed, especially 

 upwards. The posterior border is rapidly and obliquely sloped from above down- 

 wards and backwards in its upper portion, but at the lower angle is truncate and 

 bluntly rounded, this angle being the most produced part of the shell. The 

 inferior border is almost straight, but has a slight sinuosity. The hinge-line is 

 straight, equal to half the extreme antero-posterior diameter of the shell in length, 

 and if the upper and lower borders were produced forwards they would meet at 

 an acute angle. 



The umbones are small, swollen, not contiguous, situated very far forwards. 

 From the umbones there passes downwards and backwards an oblique swelling, 

 which extends almost to the posterior inferior angle ; anterior to this swelling is a 

 well-marked sulcus, which becomes broader and shallower as it approaches the 

 inferior margin. 



Interior. — As far as can be seen in fragments the arrangement of muscular 

 impressions is normal. 



The external surface is almost smooth, marked with many very fine concentric 

 lines and folds of growth, which are crowded together in front, but become 

 separated as they pass backwards, following the general shape of the shell, and 

 when they reach the oblique swelling are gradually curved upwards, so that they 

 pass iu a forward direction to the superior border. 

 Dimensions. — PI. XVI, fig. 27, measures — 



Antero-posteriorly .... 8 mm. 



Dorso-ventrally .... 4 mm. 



From side to side . . . .2 mm. 



