464 W. D. Lang — Key to some Cretaceous Po/t/zoa. 



A. Branches cyliudrical. 



I. Apertures distant (i.e. vertical distance between the apertures more than about 



four times the diameter of the aperture). 



a. Apertui-es very distant and zoaria thin. 



a. Apertures two or three in the breadth of a branch. 



1. Zoax'ia immersed. 

 a. Zoarium smuoth. 



o. Zoarium exceedingly thin and delicate ... ... ... ... 1 



/3. Zoarium not so thin and delicate ... ... ... ... 2 



h. Zoarium with transverse stri;v. 



o. Transverse stri;e faint and close 3 



j8. Transverse striiB coarser and farther apart 4 



c. Zoarium with outlines of zoa?cia marked, though the zococia are 

 not emergent. 

 a. Apertui-es arranged in pairs ... ... ... ... ... 5 



jS. Apertures irregularly arranged. 



1. Apertures very distant (6-S diameters), zooccia strictly 



cylindrical. 



a. Apertures 1-2 in the breadth of a branch. 



a. Zoarium exceedingly thin and delicate ... ... ... G 



i8. Zoarium not so thin nor delicate ... ... ... 7 



b. Apeiiures 2-4 in breadth of a branch ... ... ... 8 



2. Apertui-es not so distant (4-6 diameters), zooccia fusiform ... & 



2. Zooecia emergent. 



a. Zooecia only somewhat emergent ... ... ... ... ... 10 



b. Zocccia very emergent ... ... ... ... ... ... 11 



j8. Apertures four to six in the breadth of a branch. 



1. Apertures arranged in twos and threes (zoa?cia are shorter than in 



(leinbiata and zoa^cial boundai-ies less marked) ... ... ... 12 



2. Apertures irregularly arranged. 



a. Zooecia very emergent ... ... ... ... ... ... 13 



b. Zooccia somewhat emergent, zooecialboimdaries very clearly marked 14 



c. Zorecia immei-sed, though zottcial boundaries ai-e shown .. . ... 15 



b. Apertures comparatively close, and zoaria stout compared with diameter 



of apertures. Peristomes very high. 



o. Apertures of smaller diameter (•04--06 mm.) 16 



i8. Apertui-es of larger diameter ('US-- 12 mm.) 17 



II. Apertures close (i.e. vertical distance between the apertui'es less than about 



four times the diameter of the aperture) . 



a. Apertures two or three in the diameter of a branch. 



o. Zooecia emergent ... ... ... ... ... ... ... ... 18 



)3. Zorecia immersed .. . ... ... ... ... ... ... ... 19 



b. Apertures four to eight or more in the diameter of a branch, 

 o. Zooccia emergent. 



1. Apertures in whorls 20 



2. Apertui-es in spirals. 



a. Zooecia cylindrical ... ... ... ... ... ... ... 21 



b. Zoa?cia fusiform ... ... ... ... ... ... ... 22 



/8. Zooecia immersed. 



1. Apertures comparatively distant (2-4 diameters apart). 



a. Apertures regidarly arranged in whorls ... ... ... ... 23 



b. Apertures regularly arranged in spirals. 



a. Apertures about fom- or five in the breadth of a branch ... 24 



/3. Apertures about eight in the breadth of a branch. 



1. A transverse ridge across each zoarium just beneath the 



aperture 25 



2. No transverse ridges across the zooccia ... ... ... 26 



c. Apertures irregularly arranged ... ... ... ... ... 27 



2. Apertures close (1-2 diameters apart vertically). 

 a. Diameter of apertures 'So to •4 mm. 



o. Branches short and stumpy ... ... ... ... ... 28 



i3. Branches normal though stout 29 



