.8 QEOLOGICAL AND NATURAL IlISTORr SURVEY OF CANADA. 



Bpicuous monticules. Colls of one kind only. Cell apertures polygonal, 

 but very irregular in outline; about five are contained in the space of 

 1 mm. 



In a tangential section the coll walls appear moderately thick, with 

 numerous and conspicuous spiniform tubuli embedded in them. Wherever 

 the spiniform tubuli occur the walls are inflated, so as to make them 

 appear alternately swollen and constricted. 



Owing to the highly crystalline condition of the specimen from which 

 the species is described, the longitudinal section does not show satisfac- 

 torily this part of the structure of the fossil. The tubes, however, arc 

 seen to be traversed for a portion of their course by straight or slightly 

 curved diaphragms, and in other places the characteristic cystoid dia- 

 phragms are developed . 



This species is allied to Montlcullpora mammulala, D'Orbigny, the type 

 of the gonus; but in M. Westoni the cystoid diaphragms are not so 

 numerous, nor are they arranged in a regular series, and the smaller tubes 

 which occur in M. mammulaia arc wanting. 



Locality and Formation. — Ottawa City, Trenton Formation. 



Collector,—^, C. Weston, after whom the species is named. 



MONTICULIPORA BlLLINGSI. (N. Sp.) 

 Plate I., flgg. 2-2c. 



5^oariiim incrusting, forming a thin layer about -5 mm. in thickness. 

 External surface smooth and without monticules. Cells of one kind only ; 

 very minute, about five being contained in the space of 1 mm; Cell 

 apertures irregular in outline ; walls moderately thick. Spiniform tubuli 

 of small size and few in number occur at the angles of junction of the 

 tube-walls. 



Tangential sections show that the zoarium is composed of two kinds of 

 tabes, large and small ; the latter are very limited in number and not 

 easily distinguished. Some of the cell apertures of the larger tubes 

 exhibit in the centre, or on one side of them a perforation, due to their 

 possession of cystoid diaphragmSo The smaller tubes occupy the spaces 

 between the larger ones, and are very irregular in size and shape. 



Longitudinal sections exhibit the cystoid diaphragms in the larger tuboiS 

 mostly in their basal portionj as well as straight or slightly curved diaph- 

 ragms nearer the surface. The smaller tubes are almost indistinguishable) 

 from the larger ones. The walls of the tubes project above the sUrfixce of 

 the aoariumj so as to present in section a spiniform appearance. 



