207 



form described as Orthothetes crenistria^^ by Arthauek, the writer dares 

 not call the Chinese brachiopod by any other name than that given by Frech. 



Regarding his group 6, GiRi v says that it comprises species Devonian 

 and early Carboniferous." Ortliotetes crciiistria var. Kellii M'Cov also repre- 

 sents lower Carboniferous age. Therefore the Chinese fossil is likely also to 

 indicate a period not younger than the lower Carboniferous. In this connec- 

 tion a word may be added in conclusion. The fossil may be described some- 

 what in the following way, but not more in detail because the material is not 

 at all suited for that. 



The ventral valve is rather conspicuously concave, the beak probably 

 being twisted downwards. Hinge-line is somewhat shorter than the ma.vimum 

 breadth of the shell. The dorsal valve is v^ery strongly convex, apparently 

 somewhat flattened along the median line. The shell on the whole is wider 

 than long. Interiorly the ventral valve has the impressions ofadductores and 

 divaricatores, the latter being radiall)" striated and surrounding the former. 

 The muscular impressions as a whole have a transversely elliptical outline. 

 The twisted beak is broken away, but the divergent dental plates are shown 

 in the transverse section on the partially preserved area. The internal sur- 

 face of the dorsal valve possesses a low short median septum which longitu- 

 dinally traverses the faint muscular impressions of the adductors. The inner 

 surface of both the shells is ornamented with fine, distinct, rounded costa; that 

 fade away posteriorly, but become very distinct on the anterior and lateral 

 margins. These radial costa.^ are much more distinct in the dorsal valve than 

 in the ventral. In the marginal region narrower subordinate cost?e appear in 

 the intercostal spaces. By means of the repetition of this process there are 

 often seen three or more smaller co.stae intercalated between the larger ones. 

 In addition to these radial co.stae there are also transverse or concentric ones 

 that are very faint, and are almo-.t unrecognizable when the surface of the ca.st 

 is magnified by a lens. They are extremely obsolete on the inner 

 surface of the dorsal valve, but are somewhat stronger in the opposite valve. 

 Thus on the interior surface of the ventral valve, the visceral portion looks as 



I) Frech und Arthaber: — 1. c. 



