A NEW BRACHIOPOD, RENSSELAERIA MAINENSIS, FROM 

 THE DEVONIAN OF MAINE. 



By Henry Shaler Williams, 



Of ( 'orvfll Unirerdtij, lihacxi, Nnv York. 



In the discussion of the fauna of the Chapman sandstone of Presque 

 Isle Brook, Edmunds Hill, and other localities in Chapman Count}', 

 Maine, I referred to one of the most conspicuous and common fossils 

 of the fauna under the name '"'' Rensselaer la {Beachia) n. s., cf. B. sues- 

 .s'tt^itt," and there made the following remark: 



The abundant and great development of the Rensselaeria is a notable feature of the 

 fauna. The specimens are provisionally referred to R. suessana, which they most 

 nearly approach among the American forms in generic characters. Comparisons with 

 the figures of Terebratula trigiceps, referred by Keyser and others to Rensselaeria, as 

 well as study of the faunal associates, leads me to the opinion that the Maine speci- 

 mens may be identical with the European forms. The name Rensselaeria mainensis 

 is provisionally proposed for the form. " 



As the material was further studied and illustrations of it were 

 being prepared, the expectation was strong that the species would 

 prove to be only an extreme variety, due to shell thickening of a 

 species such as R. (B.) sftessana or B. (B.) ovalis. Comparison has, 

 however, brought to light no described species to which it may be 

 referred, and its specific characters I now believe will stand. The 

 shell is thick and massive and in its general form it resembles Rensse- 

 laeria {Beachia) suessana. It is much developed at the beak of the 

 pedicle valve; the shell substance of the umbonal region of the pedi- 

 cle valve is greatly thickened, and the cardinal margin is raised and 

 produced into a distinct flattened pseudo-area in the plane of the edge 

 of the valves. If it Avere not for the fact that the genus Renssel- 

 aeria, occasionally, has a distinct flattening of the area which is clearly 

 represented in some figured specimens and is shown on plates of the 

 several species, a new genus might be erected for this character. In 

 the revised description of Rensselaeria and of the subgenus Beachia, 

 Hall and Clarke distinctly refer to this feature. In the description 



« Contribution to the Geology of Maine, Williams and Gregory, U. S. Geol. Sur- 

 vey Bull. No. 65, 1900, p. 80. 



Proceedings U. S. National Museum, Vol. XXXII— No. 1527. 



267 



