GENERA OF CHyETETID^ AND MONTICULIPORID^. 321 



not yet submitted to microscopic examination the forms from 

 the Lower Silurian rocks of North America which have usually 

 been known to American palaeontologists as M. pulchella or 

 ChcBtetes pulchellus ; but I suspect they will prove to be distinct 

 from the British Upper Silurian examples, which are the true 

 type of the species). 



Monticulipora (Monotrypa) undulata, Nich. 

 (PI. XIV., figs. 3-3/., and 4-4^.) 



ChcBtetes undidatus, Nicholson, Geol. Mag., Dec. ii. vol. ii. p. 176, 1875. 

 ,, undulattis, Nicholson, Rep. on the Pal. of Ontario, 1875, PP- 1O5 ZZ^ 

 PI. IV., fig. I. 



Spec. Char. — Corallum forming large lobed or laterally in- 

 dented masses, or occurring as smaller hemispherical or spher- 

 oidal masses, of from half an inch to more than an inch in 

 diameter. Corallites uniformly thin - walled, angular, and 

 prismatic in shape, sub-equal in size, varying from one-fifth or 

 one-sixth of a line up to a quarter of a line or rather more. 

 The bulk of the corallum is made up of corallites of the smaller 

 of the above dimensions, while the slightly larger tubes form 

 clusters of six or more, which appear on the surface as patches 

 or " monticules," which are but faintly or not at all elevated 

 above the general level. Tabulae horizontal, complete, remote, 

 equally distributed through all the tubes of the colony, and 

 often placed at corresponding levels in contiguous tubes, so 

 that the corallum breaks up into a series of concentric strata. 



Obs.—T\i^ type of this species is a large and massive coral, 

 which occurs in the Trenton Limestone of Canada. With this 

 I formerly associated certain large and lobate MoiitiaUiporcB 

 from the Cincinnati group of Ohio and the Hudson River for- 

 mation of Canada, similar in form to some of those included by 

 Hall under the name of Chcstetcs lycoperdoji, Say (Geol. Mag., 

 Dec. ii. vol. ii. p. 177). I have not yet had the opportunity of 

 examining these latter forms microscopically, but I imagine 

 that I shall find I was in error in associating these with the 



X 



