NEOZOIC INVERTEBRATES 103 



probably not greater than that between the Chickasawan 

 and Claibornian horizons in the standard Alabama column, 

 to which we are accustomed to refer our correlations of 

 the Eocene horizons of the east American Tertiaries. 



Five species were obtained from the lower beds, one 

 being the Venericardia planicosta Lamarck, the well 

 known ' ringer post of the Eocene ' which, with two others 

 of the five, was also obtained from the upper beds. 



Owing to the poor condition of the fossils and the fre- 

 quent deformation of the casts by shearing, a number of 

 the species are here determined only generically, it being 

 thought best to defer naming specifically material which 

 might lead to confusion when better specimens turn up at 

 some future time. 



As is natural, a large proportion of the species appear 

 to be new, and of these eleven seem to be in condition 

 which renders it safe to describe and name them. 



An enumeration of the fauna obtained by Dr. Palache 

 now follows. 



LIST OF THE INVERTEBRATE FOSSILS 



PORIFERA 



Cliona alaskana Ball. 



Locality. Upper beds, 3373. 



The numerous oysters which occur in the tough greenish-black 

 shales of these beds are frequently dotted with minute circular holes 

 closed by matrix. On breaking them open the interior of the shell is 

 seen to be excavated by numerous inosculating galleries, sometimes 

 merging into irregular cavities with rugosely curved walls. These are 

 the work of the sponge Cliona which, in its younger stages, forms 

 these burrows in the shell, the water and the food it bears finding 

 access to the sponge through the small circular orifices above men- 

 tioned. In the absence of the sponge itself or its spicules it is of 

 course impracticable to enumerate distinctive specific characters, but as 

 the borings are quite recognizable and the species was doubtless dis- 

 tinct from the recent Cliona sulfur -ea, it may for convenience of refer- 

 ence take the name Cliona alaskana. 



