i6o THE GENUS MONTICULIPORA. 



sizes, their tabulation being more uniform than is usual in the 

 genus. The small corallites are, however, always to some ex- 

 tent, and sometimes quite conspicuously, more closely tabulate 

 than is the case with the large tubes. 



Though many other species resemble M. petropolitana, 

 Panel., in general form and external aspect, I know of none 

 which could be confounded with it, when it comes to a com- 

 parison of thin sections. The types which, on the whole per- 

 haps, are most like M. petropolitana, are forms like M. i^Mono- 

 trypa) Winter i, Nich., M. {Monotrypa) undulata, Nich., in 

 some of its varieties, and M. {Monotrypa) petasiformis, Nich. 

 In all these types, however, there is the important difference, as 

 compared with ]\I. petropolitana, Pand., that there is no proper 

 series of small tubes interspersed among the ordinary corallites 

 of the colony, wdiile all the corallites are similarly and uniformly 

 tabulate. 



Horizon and Locality. — Lower Silurian (Chasmops Lime- 

 stone), Ostrogothia, Sweden. Collected by Dr Lindstrom. 



Monticulipora (Diplotrypa) Whiteavesii, Nicholson. 



(Fig. 3I-) 



Chcetdcs pdropolitanus (pars), Nicholson, Quart. Journ. Geol. Soc, vol. xxx. 



p. 510, PI. XXX. figs. 5, 5r, 1S75. 

 ,, petropolitaiiiis (pars), Nicholson, Pal. of Ohio, vol. ii. p. 204, PI. XXI. 



figs. 14, 14^, 1875. 

 „ pdropolitanus (pars), Nicholson, Ann. Nat. Hist., ser. 4, vol. xviii. p. 



88, PI. V. fig. 6a {not PI. V. fig. 6), 1876. 

 „ pdropolitanus (pars), Nicholson, Geol. Mag. Dec. ii., vol. ii. p. 175, 



1875- 

 „ pdropolitanus, Nicholson, Rep. Pal. of Ontario, p. 10, PI. IV. figs. 3 

 and 4, 1875. 

 Monticulipora {Diplotrypa ) Whiteavesii (pars), Nicholson, Pal. Tab. Corals, 

 PI. XIII. figs. 4-4^— w/ PI. XIV. fig. I. 



Spec. Char. — Corallum discoid when young, hemispheric 

 when adult, often with the lateral margins widely extended, 

 the base being usually deeply concave, sometimes flattened, 

 and being covered by a concentrically striated epithecal plate. 



