76 IOWA ACADEMY OF SCIENCES. 



characteristics until in the common form the presence of cal- 

 cite would not be suspected, and the surface of the cones, 

 instead of showing clearly the individual calcite needles sharply- 

 terminating, has only a peculiar crinkled or roughened appear- 

 ance. 



Owing to the very strong crystalizing force known to be 

 possessed by calcite, so powerful an influence is exerted by this 

 substance in solution, which is manifestly at the point of satu- 

 ration, though distributed rather sparingly through the clay 

 layers, that even the clay is pressed into the form assumed 

 under normal conditions by the calcite. The process and results 

 are not unlike those which have taken place in certain sand- 

 stone beds in central France, in which calcic carbonate has 

 crystalized in the sand, and large perfect models of sand 

 cemented by lime are found, having the well formed and char- 

 acteristic crystalographic faces of calcite. 



TWO REMARKABLE CEPHALOPODS PROM THE UPPER 



PALEOZOIC. 



BY CHARLES R. KEYES. 



There have been recently discovered in the coal measures of 

 Mississippi basin some excellently preserved remains of Cepha- 

 lopods, which are remarkable on account of the huge size 

 attained. Both are representatives of the retrosiphonate Nau- 

 toidea; but one is a member of the most closely coiled end of 

 the series, while the other is a perfectly straight form. The 

 former belongs to the genus Nautilus and the latter to 

 Orthoceras. 



The first group comprises a series of shells, which were 

 obtained from the upper coal measures at Kansas City, Mo. 

 Several unusually fine specimens are the property of M. S. J. 

 Hare of that place, and others are in the possession of other 

 collectors. The form was originally described by White* 

 as Nautilus ponderosus, the diagnosis of which is essentially as 

 follows: 



*U. S. Geol. Sur., Nebraska, p. 236, 1872. 



