FAUNAS AND CORRELATIONS 313 



An unidentified coral that resembles Chcetetes milliporaceous, of the 

 Pennsylvanian of the Mississippi Valley, is a disturbing element in draw- 

 ing positive conclusion, but we do not attach great importance to it. 



Blackwelder's list of Amsden species from the Gros Ventre Mountains 

 contains no species identified by us from the AVind Eiver. However, our 

 Composita trinudea may be the same as his C. subtilita as Compositas, 

 scarcely to be distinguished, range from the Amsden to near the top of 

 the Embar (Permian). Froductus nebraskensis of the Gros Ventre may 

 be the same as the form identified by us as PustuJa genevievensis. Schizo- 

 pJioriu aff. resupinoides may be our S. swallovi. 



The e\idence of the fossils indicates that the Wind River Amsden is 

 probably older than the Gros Ventre Amsden. It is possible that the two 

 were contemporaneous, but that the Wind River basin was connected with 

 the interior basin and the Gros Ventre was not. 



Description op Species . 



ZAPHRENTI8 AMSDENENSIS n. sp. 



Plate 19, figures 19-20 



Corallum horn-shaped, circular in cross-section, slightly curved, sides 

 diverging at an angle of about 30 degrees. Surface marked by incon- 

 spicuous wrinkles, unequally spaced. Calyx shallow; fossula indistinct 

 on the shorter, concave side of the corallum; septae averaging 36, ap- 

 proaching the center in pairs, but leaving a small central area clear. 



Dimensions of largest specimen collected: Length, 51 millimeters; 

 diameter, 24 millimeters; average specimens, length, 35 millimeters; 

 diameter, 15 millimeters; smallest specimens, length, 11 millimeters; 

 diameter, 8 millimeters. 



Z. amsdenensis differs from Z. pellamsis, probably the most closely re- 

 lated species, in the al)sence of spines, smaller angle of divergence of the 

 sides, and less conspicuous fossula. From Z. dceli Milne Edwards and 

 Haime, another closely related species, it differs in the absence of spines 

 and the less conspicuous fossula. 



CHMTETES ? 



Three fragments of a form resembling Chcetetes milliporaceous were 

 collected. The best preserved specimen is silicified and details of struc- 

 ture are obscure or absent. No connecting pores have been observed. The 

 small size of the corallites and their angular shape, triangular to hexa- 

 gonal, give the species a cl(^se resemblance to Chcetetes milliporaceous. 



XXIV — BtiLL. Geot.. Soc. Am., Vol. 29, 1917 



