Geol.— Vol. I.] SMITH— COMPARATIVE STRATIGRAPHY. 405 



have made no distinction between the two groups. But 

 since the two groups have a rather distinct stratigraphic 

 range, and since the extremes can easily be separated, the 

 writer prefers to give at least subgeneric rank to Daonella. 



Daonella dubia Gabb. 



Plate XLIV, Fig. 5. 



1864. Halobia dubia, Gabb, Pal. Calif. Vol. I, p. 30, pi. v, figs. 28 a-b. 



1874. Daonella dubia, Mojsisovics, Ueber die Triadischen Pelecypoden- 

 Gattungen Daonella und Halobia, p. 22. 



1877. Halobia ( Dao7iella) lomnieli. Meek, U. S. Geol. Expl. Fortieth Paral- 

 lel, Vol. IV, p. 100, pi. X, fig. 5. 



This species, which Meek united with Daonella lomnieli, 

 differs from the Alpine form in the coarser ribs bundling in 

 pairs, instead of in threes or more. The concentric wrin- 

 kles are stronger, and the beak is higher, projecting above 

 the hinge-line. There is no ear on the shell, but the hinge- 

 line is long and straight, and near it the ribs become fainter. 

 The height is about two-thirds of the length, as is the case 

 with D. lonimeU. The greatest length observed was about 

 eighty millimeters. The figure given by Gabb is of a 

 negative cast, reversing the ribs and interspaces, and thus 

 not giving a correct idea of the ornamentation. Meek's 

 figures are correct, but his specimens were poor. 



Daonella dubia is nearest to D. faucicostataTomi\pS.^\.^ 

 from the zone of Ceratites nodosus, but is more highly 

 arched, and has a more prominent beak. The radial fur- 

 rows of D. paucicostata begin at from five to nine millime- 

 ters from the beak, and the ridges are said to be simple, 

 without bifurcations. Tornquist's figure 2 looks very like 

 D. dubia, but his description does not agree. D. indica 

 Bittner'^ resembles D. dubia, but has no bundling of the 

 ribs, which are also slightly finer, and the concentric 

 wrinkles coarser. Daonella conf. indica, Bittner^ is nearer 

 to D. dubia, and might even be identical with it. 



iZeitschr. Deutsch. Geol. Gesell., 1898, Bd. L, Heft 4, (II Beitrag), p. 673, pi. xxii, figs. 

 1-4. 

 * Pal. Indica, Ser. XV, Vol. Ill, Part 2, p. 39, pi. viii, figs. 4-11. 



3 1,. c. pi. viii, fig. 12. 



