95 



Mr. Hall, that it is G. Pitcheri, var. navia. These examples will 

 suffice to show the accuracy of the Paleontolofjy of vol. iii. of the 

 Pacific Railroad Exploration. 



We will now pass to the first volume of the United States and Mexi- 

 can Boundanj Survey. In the chapter by T. A. Conrad, Descriptions 

 of Cretaceous and Tertiary Fossils, page 141, this learned paleontol- 

 ogist describes, at page 155, the Gryphcea Pitcheri, plate vii., figure 3, 

 and plate x, figure 2. In the synonymy, he gives Gryplicea Pitcheri, 

 Morton, which is right, for it is the species which he figures under the 

 number 3 a, 3 b, representing, as Morton does, a young individual of 

 thg species.* Conrad gives also as synonym my Gryplio^a dilatata 

 var. Tucumcarii such as is represented in figure 3, or elongated variety, 

 in the Bulletin de la Soc. Ge'ol. de France. This is a mistake, and he 

 corrects it in a letter, which I will give a few lines further on. I 

 agree entirely with IVIr. Conrad, in his description of specimens 

 figured. Plate vii., figure 3 a, 3 b, represents a young individual, 

 and figure 3 c, 3 J, is a full-grown but broken specimen, representing 

 the common form of the Gryphcea Pitclieri; figures 3 g and 3/, re- 

 presents the smaller valve of the Gryjjhcea Piicheri. Plate x, figure 

 2 a, 2 b, represents an upper valve of the Gryphcea Tucumcarii, so far 

 as I can judge of the drawings without a description, for there is 

 none given. 



It seems needless to make a var. navia for the young individual, 

 merely to express a difference 'in age. 



Mr. Dana, in his Preview of Marcou's Geology of North America, 

 having quoted Conrad's opinion against me, I was led to inquire more 

 closely into the matter, as I have a great respect for that Paleontolo- 

 gist, and wished to discover, if possible, the reasons why such an 

 observer should hold so different an opinion of those two Gryphoem 

 from that of Deshayes, D'Orbigny, Agassiz, Pictet, and D'Archiac. 



* I have never seen Morton's original specimen. If the figure in his Synopsis of 

 the Cretaceous Group of the United States, plate XV., figure 9, is correct, it differs in 

 its general outline and in the details of botli valve?, from the young specimen of 

 G. Tucumcarii, published in my Geology of N(,rth America, plate iv., fig. 2; and as it 

 differs even more from the young specimen of G. Pitcheri, figure 6, on tlie same plate, 

 1 am led to believe that I did not meet with the true G. Pitcheri of Morton, in my 

 explorations with Captain Whipple's party. Mr. Ferdinand Roemer having the 

 opportunity of seeing in the company of the late Dr. Morton himself, the original 

 specimen at Philadelphia, I naturally followed his identification of G. Pitcheri; 

 and if Roemer has made a mistake, I was misled by his description in Die Kreidebil- 

 dungen von Texas. Thus we shall have three species of Gryplicea; 1, iheG. Tucumcarii 

 of the Jurassic rocks of Pyramid Mount (New Mexico); 2. the false G. Pitcheri, 

 of Roemer and Marcou, or the false G. Pitcheri var, navia of Conrad and Hall, of 

 the cretaceous rocks of the false Washita River (Texas), which may be called G. 

 Roemeri, in honor of its first discoverer, Mr. F. Roemer; and 3, the true G. 

 Pitcheri Morton, which I have never seen, and, consequently, on which I cannot 

 give any information as to its stratigraphical position and association with other 

 fossils. 



