O. P. Hay — Fossil Turtles in the Marsh Collection. 261 



Art. XXX. — On some Fossil Turtles belonging to the Marsh 

 Collection in Yale University Museum; by O. P. Hay. 

 (With Plates XI-XVI.) 



The present paper is the result of a study of some of the 

 extinct turtles in the collections of vertebrate fossils brought 

 together by Professor O. C. Marsh. The privilege of making 

 the investigation was first granted by the late Professor Charles 

 E. Beecher ; after his death it was renewed by the acting cura- 

 tor of the collection, Professor L. Y. Pirsson. For assistance and 

 courtesy the writer's thanks are due to all the officers having con- 

 nection with the department of vertebrate paleontology in Yale 

 University. The negatives from which several of the plates 

 have been prepared were furnished by Dr. George R. Wieland. 

 The wash drawings were made by Mr. Erwin Christman, of 

 the American Museum of Natural History. 



Further remarks on the species here treated and additional 

 illustrations will, it is hoped, be presented in the writer's forth- 

 coming monograph of the fossil turtles of North America. 



Baena marshi sp. nov. 

 Plate XI ; Text-figure 1. 



The type of this species was collected in 1889, by Professor 

 J. B. Hatcher, in the Laramie deposits of Converse County, 

 Wyoming, between Buck and Lance creeks. 



The specimen has suffered considerable damage. There are 

 present the central region of the carapace and most of the left 

 side, the greater portion of the plastron, and the matrix form- 

 ing a cast of the interior of the shell. The length of the shell 

 can be determined only approximately. It must have been at 

 least 300 mm , with a breadth of 220 mm . 



On account of the obliteration of the sutures of the carapace, 

 its structure cannot be made out. The bones along the median 

 region have a thickness of from 10 to 13 mm . The outer surface 

 is smooth. The sulci between the various dermal scutes are 

 narrow and shallow, and in many places cannot be traced. The 

 second, third, and fourth vertebral scutes varied in width from 

 64 to 70 mm . 



The posterior extremity of the plastron is missing ; hence the 

 length of the plastron cannot be accurately determined, nor the 

 form of the posterior margin. The total length, however, must 

 have been close to 260 mm . The following table presents the 

 most important dimensions. »In order that the distinctness of 

 the species from B. hatcheri, which is from the same deposits 

 and locality, may be appreciated, the dimensions of the plastron 

 of the latter are also given. 



Am. Jour. Sci— Fourth Series, Vol. XVIII, No. 106. — October, 1904. 

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