•299 



diflFerino- from the type iii being slightly higher in proportion to its length, 

 comes from the lower part of the Horsetown beds at Ono, Shasta County. 

 Associated with the Ono specimen there are a number of right valves 

 that probably belong to this species. They have about the same outline, 

 but are much less convex ; the posterior wing seems to be more narrow, 

 and the radiating lines are so small as to be inconspicuous except under 

 a lens."' 



" I think it probable," he adds, " that these fossils are identical with 

 the form" "from the Queen Charlotte Islands that has been referred 

 to the Jurassic Ai'icula (Oxytoma) nmcroiiata, M. and H. Direct com- 

 parison of the California specimens with Meek and Hayden's type, which 

 was described and figured under the name Pteria Munsteri (Bronn),* 

 shows recognizable differences in both outline and sculpture. When this 

 Jurassic form was described, the name Pteria mucronata was suggested 

 for it, in case it should prove to be distinct, but, before this work appeared, 

 Gabb had used Avicula mucronata for a Californian Triassic species ;t 

 consequently the name mucronata can not be applied to either of these 

 species, and I name the Cretaceous form in honor of Mr. Whiteaves. A 

 new name will also be given to the Jurassic species in another publica- 

 tion." (Op. cit. supra.) 



In February, 1879, the specimens that have been referred to 0. mucro- 

 nata and that are figured on Plates 31 and 33 of this volume, were sent 

 to Dr. Stanton for comparison, and in a letter dated February 15, 1889, 

 he writes as follows in regard to them. " After careful comparisons I 

 think that the originals of figures 6 and 6 6 on your Plate 33 are almost 

 certainly, and the original of fig. 9 on your Plate 31 ispi'obably, identical 

 with the form from the Horsetown beds that I referred to my Avicula 

 Whiteavesi. But the description and figure of that species were drawn 

 from a single specimen, from a lower horizon, and it may be the difierences 

 are really of specific importance. Besides the greater proportional height 

 of the Horsetown specimen, it shows a greater number of radiating ribs, 

 though that difference may be in part due to the imperfect preservation 

 of the type of A. Whiteavesi, from which the shell has been exfoliated 

 from the lower portion, where other ribs that do not reach the beaks may 

 be intercalated." 



"The sculpture of the original of fig. 6 a on your Plate 33 is so radically 

 different that it seems to me impossible to refer it to the same species as 

 the others. I should judge also that the form is quite different. "If 

 it is like the specimen figured from Devil's Lake it is certainly different. 

 As to its identity or otherwise with A. Cornueliana, judging only from 



* Palseontologj'^ of the Upper Missouri, p. 80, figs, a and b in text. 



t Geological Siirvey of California, Palaeontology, vol. I, p. 30, pi. .5, fig, 27. 



