No. 7.] WHITEAVES — JURASSIC FOSSILS. 405 



Yorkshire Lias. It is not a Tancredia, in the writer's judg- 

 ment, though its contour is not very dissimilar to a fossil doubt- 

 fully referred to that genus by Meek and Hayden, under the name 

 T. inozquilateralis ; but the latter species has a much natter 

 shell, and is more angular at the junction of the hinge line with 

 the posterior end. 



15. Trigonia Dawsoni, N. Sp. — Shell gently convex, com- 

 pressed ; outline ovately-subtrigonal ; anterior end very short, 

 broadly rounded, as is also the ventral margin ; beaks elevated, 

 recurved, anterior, subternrinal ; hinge line sloping concavely 

 downwards behind the beaks; extremity of the somewhat elon- 

 gated posterior end truncated rather obliquely. Surface of the 

 main body of the shell marked by about twelve curved, nodul- 

 ous costse, all of which commence at the margin of the posterior 

 area. The five nearest the beaks curve downwards, and termin- 

 ate at the anterior end. The middle ones, though curved, are 

 nearly transverse, and end at the centre of the ventral margin, 

 while the three last incline decidedly backwards. The posterior 

 area is marked either by crowded, transverse, regularly arranged 

 and continuous raised striae, or by coarse, irregular and broken 

 up or angularly bent, short, transverse folds. Iltasyouco River 

 and Sigutlat Lake, frequent and well preserved. A well mar- 

 ked and characteristic species, which the writer has much pleasure 

 in naming after its discoverer, Mr. G. M. Dawson. It would 

 appear that T. Dawsoni occurs also in the Jurassic rocks of the 

 western slopes of the Sierra Nevada, for on page 49 of Vol. I of 

 the "Palaeontology of California," after describing Trigonia 

 pandicosta from that locality, Mr. Meek says : — " there are in 

 the collection fragments of apparently two other species of this 

 genus. One of these is considerably larger than that described, 

 and has the costae distinctly nodose. They are, however, not 

 angularly deflected, but curved gradually forward." 



16. Astarte ventricosa, Meek. Iltasyouco River, three or four 

 rather imperfect specimens, whose specific characters are obscurely 

 shown, and whose identification is, therefore, somewhat uncer- 

 tain. They vary considerably in shape, two being rather longer 

 than wide ; in the others the height and length are nearly equal. 

 The pallial border of the test is distinctly crenulated. 



17. Astarte fragilis, Meek & Hayden. A badly preserved 

 specimen of an Astarte, from the Iltasyouco River, which 

 although much larger than the type of A. fragilis from Dakota, 



