Oti the MontiailipoToids of the Cincinnati Group. 125 



them, we wish to call attention to the fact that the external features 

 are not only relied upon by these two authors, but in some cases 

 they are the only ones considered to be of value. We shall pro- 

 ceed to show how this is the case by quoting from the descriptions 

 of various species by both Dr. Nicholson and Mr. Ulrich, as fol- 

 lows : 



"The most obvious feature which separates the latter \^Constel- 

 laria\ from the genus FisiuUpora is its possession of the conspicuous 

 star shaped monticules which adorn the surface of the corallum."* 

 This is an external feature, and one used to separate two genera- 

 Again: "It cannot be denied, however, that the separation of 

 Dekayia from Monticidipora, so far as our present knowledge goes, 

 is purely arbitrary, and is only defensible upon the ground that its 

 surface columns constitute a marked external character, by which 

 its species can be readily and conveniently distinguished as a group 

 apart. "f Here we have not a species, but one sub-genus separated 

 from another on an external feature. Again : Superficially M. 

 nodulosa is said to be "readily distinguished by its minute size and 

 the numerous well defined monticules which cover the surface. "J 

 M. o'fiealli "is readily recognized by its slender, cylindrical, smooth 

 branches, its regularly oval, vertically arranged calices, and the 

 presence of numerous interstitial apertures between the upper and 

 lower ends of the large calices. "§ In M. if-frgida?-is, the "small 

 size, apparently free habit, and nodulated surface, are well marked 

 external characters, though, according to Ulrich, the surface may 

 be nearly smooth. "|| M. qiiadrata is readily distinguished superfi- 

 cially "from other dendroid species of Monticulipora by the com- 

 monly rhombic or diamond shaped form of many of the calices, 

 these openings being then arranged in curved diagonal lines, which 

 cross each other obliquely. "^[ "In internal structure M. clavacoi- 

 dea, James, is most nearly allied to M. irregularis, Ulrich, but the 

 form of the corallum and the mode of growth afford a sufficient 

 means of separation. '■'° The peculiar helicoidal shape of Af. cal- 

 ceola, "and the fact of its being built round a curved central tube 

 which opens externally by a round aperture, would alone distin- 

 guish the species, quite apart from its -internal characters. "<z In 

 M. briarea "the peculiar form and mode of growth of the cor- 

 allum .... taken alone, would render its distinctness highly 

 probable."/; In his description of M. parasitica, which we shall 



*Nicholson. Genus Monlicu.. p. 98. 



•{-Ibid p. 99. tlbid,p. 117. $lbid,p. 119. [|lbid, p. 17S. TTIbid. p. iSo. °lbid, p. 1S5. 



albid, p. 1S6. /'Ibid, p. 199. 



