23 



In internal characters, Heterotrypa simplex resembles H. solitaria, Ulrich, 

 of the Fairmount, but this species is frondescent rather than ramose in its 

 manner of growth. From all other species of Bryozoa occurring in the Credit 

 River section, the present species may be distinguished by the very regular 

 arrangement of the acanthopores and the entire absence of mesopores. 



Locality. — Credit river, Streetsville. 



No. 12159, Royal Ontario Museum of Paleontology. 



Heterotrypa simplex maculosa, var. nov. 

 Plate III, Figure 2; Plate VII, Figure 9 



The above variety differs from Heterotrypa simplex only in the occurrence 

 of maculae. These are placed at wide irregular intervals over the surface of the 

 zoarium and are not raised above the general level of the zoarial surface. They 

 are composed of mesopores, five to twenty in number, and in certain places are 

 surrounded by zooecia larger than the average. 



In both Heteroptrypa simplex and H. simplex maculosa, quite definite 

 boundaries between the zooecia are seen in sub-mature regions, but, as 

 in Heterotrypa robusta, the walls become fused in the mature regions. 



The variety occurs in the Streetsville member, very often in association 

 with Heterotrypa simplex. 



Locality. — Credit river, Streetsville. 



Nos. 12160, 12175, Royal Ontario Museum of Paleontology. 



Heterotrypa subpulchella parvulipora, var. nov. 

 Plate VI, Figure 9 



Among the older collections of Bryozoa^ from Streetsville in the Royal 

 Ontario Museum of Paleontology, one specimen was found which closely 

 resembles Heterotrypa subpulchella (Nicholson), of the Maysville of Ohio. 

 In form it is a flattened sub-ramose mass, measuring 32 mm. in length, 20 mm. 

 in width, and 13 mm. in height. It probably branched, since the broken bases 

 of branches are still seen. Maculae are scattered over the surface of the zoarium, 

 with an average distance of one millimetre between them. They are scarcely 

 raised above the general surface of the zoarium. 



The variety resembles the type in tangential sections, particularly in the 

 character of the maculae, which consist of mesopores to the number of 10 or 

 15 in each, surrounded by zooecial tubes of distinctly larger than average size. 

 The acanthopores are numerous and vary considerably in size, some of them 

 being abnormally large. They are usually found between the angles of junction 

 of the zooecial walls. The zooecia of the new variety are smaller than in the 

 type of the species, 11 to 12 being found in two millimetres, in the former; 

 while in the latter, no specimens have been recorded in which they are more 

 numerous than nine in two millimetres, and according to Nicholson there are 

 only six to seven tubes in this distance. This is the most outstanding difference 

 between the two forms. Another difference is that in H. subpulchella parvulipora, 

 the mesopores are confined to the maculae, while in Nicholson's species they 

 are sometimes found between the maculae. 



The two forms are very similar in vertical sections. They possess thin, 

 crenulated walls, with the average number of diaphragms for the genus to 



