55 



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

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

 in such cases having somewhat the form of an houi-glass. 



Fig, 60. 



Fig. 60. — Arthroclema pulchclla. 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. 



Collectors, — E. Billings and W. Rogers. 



Also 



Stromatopora compacta. (N. sp.) 



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

 inches m 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 8. rugosa in bemg much smaller and more 

 compact. It occurs m'localities where S. 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 Paqucttc Hapids, on 

 the Ottawa river. Black River hmestone. 



Collector s.- 



-Sir W. E. Logan, J. Richardson. 



