H. M. Seely — A new genus of Chazy Sponges. 355 



Art. XL VI. — A new Genus of Chazy Sponges, Strephochetus ; 

 by Professor Henry M. Seely. 



The Chazy rocks of the lake towns of Addison County, 

 Vermont, afford a fossil form which, so far as is known to the 

 writer, has not been heretofore described. That it should have 

 been so long neglected is the more remarkable since it is an 

 excellent guide to some layers of the Chazy when other well 

 known fossils are obscure or wanting. 



The nearest approach to an illustration of this form is found 

 in the Geology of Vermont, vol. i, p. 277, fig. 175, where Phy- 

 topsis tubulosum is figured. In the text, attention is called 

 to a horizontal section of the stem ; and the concretionary ar- 

 rangement of the calcareous matter is pointed out. No per- 

 pendicular section is given. 



It was assumed on a recent examination that the form was 

 of animal origin and a provisional name indicating that it was 

 a Stromatopora was assigned it. A more extended examination 

 however does not confirm the first impression. The size of the 

 object favors its complete inspection, it being so small that a 

 section of the entire fossil cut in any direction can be placed on 

 a slide and put upon the stage of the microscope. 



The mass is seen to be mostly made up of concentric layers 

 of material, these layers being apparently composed of fine wavy 

 twining threads about - 2 \ of an inch in diameter ; but in 

 section these threads are seen to be essentially circular tubes. 

 The more exact measurement of these tubules is, according 

 to Dr. M. C. White, outside measure y^Vo inch, the inner 

 diameter, clear space, 22V o inch. The outer portions of the 

 layers seem more compact, and on weathering the fossil 

 assumes a Stromatoporoid appearance. The form is accom- 

 panied by grains having in many cases a concentric structure, 

 and these are apparently oolitic ; yet with these are mingled 

 minute fragments having the structure of the larger nematoid 

 mass. These grains, oolitic, fragmental, and possibly in many 

 cases the young of the animal, have in some instances pene- 

 trated the larger mass and partake with it the concentric ar- 

 rangement. 



In seeking the relationship of this fossil, its general character 

 shows it to be allied to the sponges. The scanty materials at 

 hand with which to make comparison do not permit me to 

 pronounce with entire confidence as to its very nearest allies. 



Sections of a fossil form, described by S. A. Miller, as Stroma- 

 tocerium Richmondense, Journal of the Cincinnati Society of 

 Natural History, vol. v, April, 1882, show here and there, but 

 rarely, a structure which is probably identical. The newly 



