LOWER SILURIC SHALES OF THE MOHAWK VALLEY 



77 



spicules being more distinct in some, the transverse in others. 

 Larger dictyonine spicules (typical hexactines), corresponding in 

 size to those of the Utica species C. reticulata ( Walcott) 

 have been found in adjoining layers, demonstrating the actual pres- 

 ence of dictyosponges in these beds. 



Fig. 14 



Fig. .13 



Fig. 13-15. Dictyonema arbuscula (Ulrich) 



Fig. 13. Small rhabdosome, x 5. Fig. 14, 15. Fragments of distal por- 

 tions of larger rhabdosomes, x 5. 

 Indian Ladder beds, at the Indian Ladder, N. Y. 



Dictyonema arbuscula (Ulrich) 

 PI. 2, fig. 15 



A small Dictyonema was found to be not infrequent in the Indian 

 Ladder shale at the Indian Ladder, which proved to be identical with 

 a species hitherto recorded only from the Eden (formerly Utica) 

 shale of the neighborhood of Cincinnati. According to Doctor 

 Ulrich this species occurs in the Middle Third of the Eden shale. 

 It was first described and figured in 1879 (title 8, p. 28) and also 



