SUB-GENUS HETEROTRYFA. 139 



NIch., of the same formation; and in treating of the latter 

 I shall point out such features as seem to render a separation 

 between these two types desirable. 



FoiDiatioii and Locality. — Not very uncommon in the 

 Hamilton Group (Devonian) of Widder, Ontario. 



Monticulipora (Heterotrypa) Barrandi, Nich. 



(PI. I. figs. 2-2rtO- 



Chcetctes Barrandi, Nicholson, Geol. Mag. Dec. II., vol. i. p. 57, PI. IV. fig. 

 7r, 1874. 

 „ „ Nicholson, Pah^ontology of Ontario, 1S74, p. 60. 



Spec. Ckar. — Corallum dendroid, or sometimes forming 

 small lobate masses, the diameter of the stems in the former 

 case varying from two to hve lines. Surface smooth, with- 

 out spines, and devoid of any marked tuberosities, though 

 exhibiting groups of corallites of slightly larger dimensions 

 than the average. Calices polygonal, thin-walled, sub-equal. 

 Corallites exhibiting a seeming complete amalgamation of 

 their walls, mostly of very uniform dimensions, averaging 

 about I -80th inch in diameter, with a few much smaller tubes 

 intercalated here and there amongst them. Small thick-walled 

 hollow tubes (" spiniform corallites ") are occasionally developed 

 at the angles of junction of the normal corallites. Tabulae com- 

 plete, horizontal, only slightly developed in the axis of the 

 stems, but moderately numerous in the peripheral portion of 

 the tubes. 



Ods. — The present species is in many respects nearly allied 

 to the preceding [III. monilifonnis, Nich.), with which it agrees 

 in its general form and aspect, as well as in the apparent 

 complete amalgamation of the walls of the ordinary corallites, 

 and in the entire absence of any proper series of small and 

 peculiarly constructed interstitial tubes (exclusive of the " spini- 

 form corallites"). The corallites, however, are of decidedly 

 smaller size ; the calices (PI. I. fig. 2a^ are more markedly 



