55 



The pores are oblong-oval about six in the length of one Ihie. In general 

 there Js, on'each side of the joint, an enlargement of the stem, the segments 

 in such cases having somewhat the form of an hourglass. 



Fig. 60. 



Fig. 60. — Arthroclema pulchcUa. A specimen of the usual size partly imbedded in 

 stone ; a, enlargement of one of the joints of the main stem and of 

 a portion of one of the branches. 



Locality and Formation. — Trenton limestone. City of Ottawa, 

 near Peterborough, Canada West. 



Also 



Collectors.- 



-E. Billings and W. Rogers. 



Stromatopora compacta. (N. sp.) 



Description. — This species forms small sub-globular masses, from 1 to 2 

 inches in diameter. The concentric lamellae are thin and closely packed 

 together, there being in some specimens from 6 to 12 layers in the thick- 

 ness of 2 lines. 



This species differs from S. rugosa in being much smaller and more 

 compact. It occurs in'localities where 8. rugosa is not found, but at Pa- 

 quette Eapids it is associated with that species in the same beds. 



Locality and Formation. — Island of Montreal, and Paquette Rapids, on 

 the Ottawa river. Black River limestone. 



Collectors. — Sir "W. E. Logan, J. Richardson. 



