EXPLANATION OF I'LATES 371 



I'LATE 12. MoiirilOLOGV UF THE TBEroSTUM ATA. 



Figure 21. — I'drlhilhi (lifnirdnniKilii- (Irairiiif/ of a IdnniltidiiKil siflioii o/' u 

 zooccium of Pniftoiiora Hiiiiilatrix. 



This is ail extromely well dofinefl brown mass with tlie cysti- 

 phragiiis dovelopc'd all aroinul the zoocciuui, as is usually the case 

 in Prasopoi-a. X 05. (11 i-1 G. ) 



Figure 22. — Sciiii-diiif/rdiiniKilic druiriini of u Joiii/il (hUikiI scdioii of <t zou-ritiui 

 of Pcioiiopora vera. 



This shows tho characlcristic succession of hrowii masses and 

 eystiphragms of this species. X 05. (112-12.) 



Figures 2o to 2(>. — 'I'uitijtiiiiul sections of Ilclciolrnpd uinl f'croiioiioia (li-iirc 



24). 



The normal appoaraucc of comiiniuicatioii iior(>s is shown in 

 these sections (^0- I'l'e wall lamin;p are cut squarely off at the 

 pores. X 287. (in,S-21 ; 147-14; 101-20; 20.) 



Figure 27. — Tan;/( hCkiI section of Ileteropora torlilis from llic Miocene of 



Petershttrn. Vti. 



The coiiimunicatiou pores, excei>t for the flaring nmudis. pre- 

 sent exact l.v the same appearance as in the Treposlomata. That 

 the douhle-funnel shape is not invariable is sliowii by the pores p 

 and ?>'. X-2S7. (118-18.) 



Figure 28. — Longitudinal section of tlie icall of Heteroin/iKi proli/icd. 



The pore presents the same appearance as in the tangential 

 section. X 287. (168-21.) 



Figure 29. — Longitudinal section of the tcall of Heterotnjpa prolipca. 



This section cuts through the wall in such a way as to cross the 

 pore in a direction somewhat oblique to the axis of the pore. 

 X 287. (108-21.) 



Figure oO. — Portion of n louf/il iidinal scclian of tlir irall of (felrropord toil it is. 



'IMie wall is cut in the same manner as the wall of IIeleroii-ypa 

 of the picccdig ligure. Some of the jiores are cut straight across 

 and some more or less obliquely. The appearances are exactly the 

 same as in figure 20. X 287. (118-18.) 



Figure ul, — A fcic grains of the brown ntutcriul of a cgst of llelerotrgpu .siil)- 

 ramosa. 



The grains have the form of minute concretions or nodqles, 

 X450. (123-4.) 



