DESCRIPTION OF PELECYPODA. 415 



Daonella (?) subjecta. 

 Loc, Sailors canyon. Coll., Dr Curtice. 



The fossils of this species are much compressed and not well preserved, 

 but they are probably referable to the genus Daonella. The outline varies 

 from an ellipse, the antero-posterior axis considerably longer than the 

 dorso-ventral, which is evidently the normal form, to an oval, wdth the 

 longest axis dorso-ventral. How much of the last is distortion due to 

 fossilization it is impossible to say, the material being very limited. The 

 shell is marked by coarse concentric ridges near the umbo, becoming 

 finer outwardly, as in Daonella and Monotis; the radiating lines are coarser 

 than in any other species of Daonella from Sailors canyon, with a finer 

 line between each pair of coarse ones. The hinge line is certainly that 

 of a Daonella, but I have used a query after the generic name on account 

 of the state of preservation of the specimens on hand, only two of wdnch 

 are whole. The radiating lines are distributed about equally over the 

 entire surface, but are more prominent near the centers of the valves. 

 These fossils were regarded by Dr Curtice as lying above the Monotis 

 shales, and this agrees with the paleontology. There were no associated 

 species in the single small slal) of black shale collected. 



^Daonella bochiformis, n. s. 

 Loc, Sailors canyon. 



This shell, as the name indicates, is a close approximation to the 

 European D. bochi of Mojsisovics from the passage beds between the 

 JVIuschelkalk and Noric series.* The umbones are nearer the center 

 than in tliat species, the concentric ridges more linear and the radial 

 marking more distinct and closely crowded. It, however, belongs to the 

 primitive type of the group which approximates closely to the ancestral 

 genus, Posidonia. The American species is, however, evidently more 

 distant from Posidonia in the genetic series and nearer the typical, heavily 

 striated forms of the genus than the European forms. Our species is 

 also probably smaller as a rule than the D. bochi. The outline is that of 

 a flattened ellipse, the lower edge being gibbous and the hinge line flat- 

 tened, the longest dorso-ventral diameter being near the center. The 

 young shells are radiately ridged at a comparatively early stage of 

 growth and the Posidonian stage is not strongly marked. A fragment 

 of this species was found associated with a species of Ammonitina? from 

 the Ammonites bed of Sailors canyon. These were for the most part 

 found below the Ammonitina3 and were accompanied by a few poorly 

 preserved Pelecypoda of several other genera. 



* Daonella and Halobia, Abh. geol. Reiehsanst., vol. vii, pi. :l, f. 1.5. 



