17 



Orthoceras lamellosum, Hall. — A single example of this species was found 

 in the Humber member in the quarry at Port Credit. It has been reported 

 by Parks and Fritz from the Humber member of the prison quarry at New- 

 Toronto, but it is not so abundant as Actinoceras crebriseptum at that locality. 

 A. crebriseptum has not yet been found in the quarry at Port Credit, but its 

 presence there is to be expected, since it is so abundant in the prison quarry at 

 New Toronto, which occupies practically the same stratigraphic level. In 

 New York, O. lamellosum is found in the Pulaski shales. 



Trilobita 



Calymene sp. — An indeterminate specimen belonging to this genus was 

 found among the collections at the University, labelled as coming from the 

 Richmond of Streetsville. 



•> Isotelus maximus, Locke. — Fragments of Isotelus probably belonging to 

 the above species occur at many horizons in the Dundas formation and in the 

 Erindale member of the Richmond in the Credit River section. It is most 

 abundant in the Credit member of the Dundas where it is found incrusted with 

 the zoaria of Stigamatella sessilis crassa. Some of the fragments occurring in 

 this member are very large. On comparing the measurements of some of the 

 largest fragments found with corresponding fragments of the large forms of the 

 Don Valley brick yard, it was found that the specimens from the Credit com- 

 pared favourably with the largest forms from the Don. 



Incertae Sedis 



Pasceolus cf. camdenensis, Foerste. — The impression of part of the external 

 surface of a specimen of Pasceolus was found at the foot of the cliff at Section 

 No. 12, near Streetsville; it came either from the Erindale or Streetsville member 

 of the Richmond, parts of both members being exposed at this locality. The 

 impression of the plates is very distinct and shows that the plates were convex 

 when looked upon from the .exterior as in P. camdenensis. 



DESCRIPTION OF NEW SPECIES 



Amplexopora solitaria, sp. nov. 

 Plate I, Figures 1 and 3; Plate VII, Figure 2 



This species is represented by one small fragment of a ramose zoarium 

 from the Homotrypa streetsvillensis zone of the Streetsville member. The 

 surface of the specimen is so thickly covered by limestone that its character 

 can scarcely be seen, but it is apparently smooth. 



In tangential sections cut from the mature zone, it is seen that the zooecial 

 tubes, which average eight in two millimetres, have extremely thick walls, as 

 much as two-fifths of the diameter of each tube being taken up by the walls. 

 A peculiar feature, however, is that at certain places the walls become thin as 

 if monticules had been cut through. In tangential sections, the dark boundary 

 between the walls of the adjacent tubes is not always seen, but in deeper tangential 

 sections it is clearly marked. Mesopores are numerous and are usually found 

 scattered throughout the zoarium. The arrangement of the acanthopores is 

 much the same as in Heterotrypa robusta (see p. 22). They are found between 

 the angles of junction of the zooecial walls, usually inflecting the latter. 



2 S.P. 



