72 



between the specimeuB trom the two localities ; but, as has already been 

 pointed out, the exact nature of the surface ornamentation of these from 

 the islands in Skidegate Channel has yet to be ascertained. 



Distorted examples, like that from which figure 2a on Plate X. was 

 drawn, might be mistaken for the Oregon species doubtfully referred by 

 Gabb * to the T. Gibboniana of Lea ; but the normal shape of the two 

 shells is quite distinct. The specimens described by Dr. Lea and Mr. 

 Gabb clearly belong to the section Quadratfe, while the Queen Charlotte 

 Island fossils would be more correctly placed among the Clavellata), 

 which by some writers are united with the Scaphoidea. 



ToLDiA. (Sp. undt.) 



Compare Yoldia nasiita, Gabb. " Paliuoutology of California," Vol. I., page 216, Plate 

 XXXII., fig. 287, and Vol. II., pages 58 and 103. 



Shell, or rather cast, compressed, moderately thin, elongated; beaks 

 prominent, recui-ved, jilaced a little in front of the middle. Cardinal 

 margin slightl}^ convex, sloj)ing gently downwards in advance ; concave, 

 and at length cm-ving upwards behind. On the cast, a blunt ridge, 

 which extends from the beaks to the tip of the posterior extremity, 

 marks out a lanceolate, escutcheon-like depression, and a similar but 

 more acute ridge in front, defines anothei area of the same shape, which 

 represents the lunule. These appearances, however, are j)robably due 

 to the thickening of the hinge plate on ouch side of the ligament for the 

 recej)tion of the teeth. Margin of the anterior end narrowly rounded 

 or subangular about the middle ; ventral border broadly rounded, but 

 curving upwards more decidedly behind than in front; posterior end 

 moderately produced, narrow and bluntly ])ointed above. 



Surface marked with very fine and close set concentric striations, 

 which arc scarcely visible without a lens; hinge teeth numerous, not 

 very small; pallial impression undistinguishable. 



Greatest length of the only sjDecimen, about three and-a-half lines ; 

 height, from beaks to base, rather more than two lines; thickness 

 through the valves, not quite one line and-a-half. 



A solitary cast of a probably immature individual, with a small 

 portion of the test jweserved on one of the valves. 



The posterior end of the present fossil is narrower, and more pointed 

 above, than is the corresponding part of Yoldia nasuta, and at present 



" faloBontology of California," Vol. I., page 190. Plate XXV., fig. 178, and Plate XXXI., flg. 202. 



