6 AMERICAN GEOLOGY. «to Gryphcea dilalata var. Tucumcurii, is the true G. Pitcheri «Morton, and the oyster you refer to 0. Marshii, we think «the same as O. subovata of Shumard. Dr. Geo. G. Shumard «says: G. Pitcheri (meaning the true Pitcheri of Morton) ranges «through the whole series of the Cretaceous formations of Texas «and New Mexico (see: Trans. St. Louis Acad. Sc., vol. I, N° 2, «p. 289): all the other explorers of that region I have seen «tell me the same. You will bear in mind Dr. Shumard in «speaking of G. Pitcheri, refers to the peculiar form you re- «gard as G. dilalata, which you may see is exactly the type « of the original G. Pitcheri figured by Morton. The shell you «and Ferdinand Roemer figured as G. Pitcheri is now regarded «by all in this country who have given much attention to the sub ject, as a distinct, and unnamed species.® I will answer your objections as briefly as possible and try to be clear and precise in my meaning. First. — I would say that, before coming to a final conclu sion with regard to the determination of the Gryphcea dilalata var. Tucumcarii and the Ostrea Marshii, I consulted all the books on the subject: Morton’s Synopsis of the Cretaceous etc., Roemer’s Die Kreidebildungen von Texas, and Shumard’s Pale ontology of the Red river of Louisiana. The figure in Morton’s Synopsis, pi. 15, fig. 9, is not good, and the text is very un satisfactory, so that I do not think it is possible to determine exactly what Morton means by his G. Pitcheri, with only his book in hand. Roemer gives a very good description of the G. Pitcheri, p. 73 and 74, and his figures are tolerably good, especially fig. 1 c; Roemer says that he has seen at Phila delphia the original specimens of Morton, but that they were very imperfect and he found it difficult to identify them with his own specimens; notwithstanding which, he does so and says they are the same species, which he calls G. Pitcheri. In Shumard’s Paleontology of the Exploration of the Red river of Louisiana, the descriptions of fossils are excellent, but the fig ures are miserable and cannot be of any use for comparison. In saying this, I wish it to be understood that I do not intend