CRETACEOUS FOSSILS. 209 



DOUBTFUL SPECIES. 



FIGURE 197, plate 26, and figure 275, plate 31, represent inte 

 resting forms, which I have been unable to refer to any genera 

 with certainty, from not being able to expose the hinges. Figure 

 198, plate 26, is probably a Trigonia ; but I have deferred further 

 determination until more perfect specimens shall have been dis 

 covered. It has been found at Orestimba Canon, Stanislaus 

 County; Cottonwood Creek, Shasta County; and Jacksonville, 

 Oregon. The shell figured at 197 is from Martinez, and is very 

 rare. Figure 275 is from a Mactra-like shell ; but, from the re 

 mains of the impression of the hinges on the matrix, it seems to 

 have had two or three heavy cardinal teeth, and to have wanted 

 entirely the cartilage-pit of that genus. Two specimens were 

 found at Marsh's, east of Mount Diablo. 



Besides these, there are imperfect remains of twenty or thirty 

 species in the collection of the Survey, of which I have not suf 

 ficient material for determination. One of the most interesting 

 is a single Echinoderm, belonging apparently to the Spatangidce, 

 the only representative of the class yet discovered in the forma 

 tion in California. It was found near Clayton by Mr. Bromley, 

 and is in too imperfect a condition for determination. 



PAL. VOL. I. 27 



