502 PROCEEDINGS OF THE ACADEMY OF [Dec, 



beds appear to be higher in the formation than those at the Spill- 

 way excavation. The fossils are pelecypods mostly and are similar 

 to those in the upper part of the excavations for the Locks at Gatun 

 as well as those from the Spillway. The material in which the 

 shells are imbedded is mostly volcanic ash, often hardened by the 

 calcium carbonate from the shells, which in their turn are partly 

 dissolved and softened, falling out of the rock as casts of the interior 

 of the shell and leaving a more or less perfect mould. The species 

 identified are as follows: 



Turritella altilira Conrad. 



Turritella gatunensis Conrad. 



Area dariensis B. and P. 



Cardium stir latum B. and P. 



Cardium dominicense Dall. 



Chione tegulum B. and P. 



Chione ulocyma Dall. 



Callocardia gatunensis multifilosa Dall. 



dementia dariena (Conrad). 



Cyclinella gatunensis Dall. 



6. Fossils from the fossiliferous layers near Tower N, Las Cascades, 

 Culebra Cut. At Las Cascades the Culebra Cut passes through a 

 hardened volcanic ash or tuff, interbedded with which are several 

 thin, fossil-bearing layers. The uppermost of these is some 85 feet 

 above the bottom of the cut, as it was at the time this collection was 

 made. It is a thin limestone bed, often not more than a few r inches 

 thick. This we have called the Pecten bed, from the numbers of 

 Pecten and Amusium which it contains. This Pecten bed was seen 

 by Professor Scott to extend along the cut to about a mile south of 

 Empire, or at least two miles along the cut. The material of the 

 bed is largely ash which is cemented to a firm stone by the calcium 

 carbonate derived from the shells, which in many cases are dis- 

 solved, leaving a mould or cast. The list of species found in 

 this Pecten bed includes several species found at the Spillway as 

 well as at the Lock excavations at Gatun, along with several new 

 species. The list of species identified from the Pecten bed is given 

 below. 



At 65 feet below the Pecten bed, and also at some 20 feet still 

 lower, or what was the bottom of the cut when this collection was 

 made, are black lignitic clays interbedded with the gray tuff which 

 carry a fauna of small molluscan forms. These represent a 

 dwarfed or 'runt' fauna such as is often found in connection 

 with lignitic formations. There are also remains of Crustacea, 



