RECORDS. 687 



Summary of Papers. 



Professor Dean referred to the purchase of the Jay Terrell 

 collection of fishes, by Mr. William E, Dodge, and his presen- 

 tation of the same to the American Museum. Dr. Dean spoke 

 of the great interest of this material, and described two new- 

 forms of Placoderms now in the paleontological museum of 

 Columbia University. The new forms resemble, in the character 

 of their "jaws," the long known Callognathus. In one favorably 

 preserved " jaw " the rounded and tooth-bearing margin suggests 

 the condition in Diplognatlms. In one specimen the shoulder 

 armoring is particularly narrow antero-posteriorly. Several der- 

 mal plates are present which are unknown in the anatomy of 

 Coccosteiis, and their definite position has not been determined. 

 The so-called " pectoral spines," described by Newbeny, and re- 

 ferred to by other writers, are now to be regarded as belonging 

 in the region of the mouth. A specimen of one of those in 

 the Terrell collection, presents a well-marked tooth on its margin. 

 In a newly acquired specimen a portion of the body investiture is 

 preserved, which exhibits a smooth surface, from which arise 

 conical eminences in somewhat definite rows, resembling those of 

 AncJienaspis {Thyestes). Dr. Dean referred also' to the mode of 

 occurrence of the Placoderm-bearing concretions in the Cleve- 

 land shales. In the region near Linville, Ohio, on the testimony 

 of the veteran collector. Rev. Dr. William Kepler, of Clyde, 

 Ohio, the following arrangement maintains. At the base of the 

 shale are found the smaller species of DiiiicJitliys {D. gouldi, and 

 D. intcrniediiis ?). Above this is a layer of flag stone ten feet 

 in thickness. Overlying this occurs a narrow seam in which 

 are sharks, Titanichthys and Mylostoina. After an intei"vening 

 seam, two feet in thickness, a wide band of the shale contains 

 DinichtJiys and TracJiosteiis. At the top of this shale, after 

 another intervening (sandstone ?) seam, in a layer of 20 to 30 

 feet thickness, 'which yields sharks, occur large specimens of 

 DinichtJiys, and the forms referred to in the present communi- 

 cation. 



