No. 1797. 



NEW TUBULIPOROID BliYOZOA—BASSLER. 



508 



bryozoans have a similar geologic distribution. Stomatopora, Pro- 

 hosciTia, Berenicea, and other genera, although well developed before 

 and after, have no known representative during Carboniferous time. 



VARIATIONAL FORMULAS. 



The extreme variabihty of these simple Cyclostomata has been 

 recognized by many writers, with the result that the conception of a 

 species has often changed with each author's study. Gregory has 

 recognized this variation and has suggested the identification of 

 species by means of variational formulae. For the simple, inc rusting 

 forms, such as those discussed in this paper, he uses four main features, 

 namely, the character of the peristome, the shape of the zooecia, the 

 length of the zooecia, and, finally, the general aspect of the zoarium. 

 Thus, for Stomatopora, the terms of his formula are as follows: 



Applying his method to Stomatopora dichotoma (Lamouroux), 

 illustrated on page 499, its formula would be as follows: 



p. c. I. r^ 



2"o 1 r 



Stomatopora dichotoma (Lamouroux) 



However, a new scheme would be necessary for the species formerly 

 assigned to Stomatopora but here described as Corynotrypa, since two 

 of the terms — the length and outhne of zooecia, including the stolon — 

 vary considerably in the same species, and the two remaining terms, 

 the peristome and the zoarium, are practically always the same. 

 For example, the formula for Corynotrypa inflata, as illustrated in 

 figures 12 and 13, would be as below: 



V' 



Corynotrypa injlata (Hall) = y 



I. 



1-2-3 0-1-2-3 







Of course it is recognized that the latter is an extreme case and 

 that the formula for this species should be based upon normal zooecia 

 only, as shown in figure 2d. The terms of the formula quoted above 

 probably will serve very well for species of the genus Stomatopora as 

 here restricted. 



For Corynotrypa, it is believed that a division into three sections, 

 based mainly upon the angle of divergence of the zooecial walls, is 

 preferable and of more value in the identification of species. 



