298 



Anterior side consisting only of the anterior alation, which is narrow 

 in the direction of its height or depth : posterior side widening or rather 

 increasing rapidly in height backward : posterior end broadly, concavely 

 and rather deeply emarginate at about the midheight, produced and ap- 

 parently somewhat pointed below : posterior wing extending nearly or 

 quite as far backward as the central portion of the valves : inferior mar- 

 gin forming a long oblique and broadly sigmoidal curve backward and 

 downward from the anterior to the posterior end : cardinal margin 

 straight, horizontal, extended, and forming the longest part of each valve : 

 umbo and beak attenuate, the latter slightly depressed, appressed, pointing 

 forward and placed at a short distance from the anterior end. 



Surface apparently almost smooth and marked only by concentric 

 striae of growth. Cartilage pits numerous and well defined. 



North side of Maud Island, about a quarter of a mile from Gold Har- 

 bour Village, C. F. Newcombe, 1897 : a nearly perfect cast of the interior 

 of both valves, with a portion of the test preserved on the left valve. 



The species seems to be well characterized by its peculiar shape, and 

 more especially, by its largely developed posterior wing, by its narrowly 

 produced anterior alation, and extended cardinal margin. 



AvicuLA (Oxytoma) Whiteavesi, Stanton. 



Oxytoma mucronata, Whiteaves. 1884. This volume, pt. 3, p. 238, pi. 31, fig. 9, and 

 p. 251, pi. 33, figs. 6, and 6b ; but not Avicula mucronata, Gabb, 

 1864, as pointed out by Dr. Stanton ; and probably not Pteria, or 

 Avicula, mucronata. Meek and Hayden, 1864, which is said to be 

 a Jurassic species. 



Avicula (Oxi/toma) Whiteavesi, Stanton. 1896. Bull. U. S. Geol. Surv. Terr., No. 133, 

 p. 38, pi. 4, fig. 1. 



East side of Alliford Bay, Skidegate Inlet, Dr. G. M. Dawson, 1878: 

 the left valve referred to on page 238 and figured on Plate 31 of the third 

 part of this volume. Both in outline and sculpture it is remarkably 

 similar to the shell figured as Fteria Munsteri on page 80 of Meek and 

 Hayden's Pal;>?ontology of the Upper Missouri, which they suggested 

 might be called Pteria mucronata or A%ncula mucronata. 



The specimens from the " Lower Sandstones" of the south side of Maud 

 Island, that were referred to Oxytoma mucronata on page 251 of the 

 third part of this volume (with the exception of the original of fig. 6 a on 

 Plate 33 of the present part), are also now believed to be referable to A. 

 (0.) Whiteavesi. 



Dr. Stanton says that his original description of A. Whiteavesi was 

 "drawn from a single specimen found with Aucella crassicollis, etc., in 

 the upper part of the Knoxville beds on Shelton ranch, five miles north 

 of Paskenta, Cal. Another left valve referred to the same species. 



