A. 'profundus the septa are -svell developed, and give to tlie fossil the aspect 

 of a Petraia or Zajjhrentis. It may be that these two species should be 

 placed in different genera ; but as there are numerous fragments of what 

 appear to be intermediate forms, it would seem to be the better course to 

 group them together in the first instance. 



Archeocyathus profundus. (N. sp.) 



.4. Minganensis, pars, as published in 1861. 



Fig. 1. 



Fig. 2. 



Fig. 3. 



Fig. 1. — The slender base of attachment. Fig. 2. — A longitudinal section through 

 the base of the cup of a woi'n specimen ; a, a transverse section of a fragment where 

 the diameter of the cup is 3h inches, showing the radiating septa between the outer and 

 inner walls. Fig. 3. — A transverse section across the base below the bottom of the 

 cup. 



Fig. 4.— Fragment of an individual which is 3J inches in diameter, showing the 

 annulations and the septal striae. 



