200 THE GENUS MONTICULIPORA. 



Monticulipora (Monotrypa) tuberculata, Milne-Edwards and Haime. 

 (PI. IV. figs. 2-2d) 



Chcctdes iiiberciilatus, Milne-Edwards and Haime, Pol. Foss. des Terr. Pal., 



p. 268, PI. XIX. figs. 3, 3^-, 185 1. 

 Chcetdes corticatis, Nicholson, Quart. Journ. Geol. Soc, vol. xxx. p. 512, PI. 



XIX. figs. 13, 14, 1874. Pal. Ohio, vol. ii. p. 210, PI. XXII. figs. 6, 6«. 

 Chistetes iiiberciiiaius, Nicholson, Ann. Nat. Hist., sen 4, vol. xviii. p. 91. 



Spec. Char. — Corallum parasitic, forming a thin crust, gener- 

 ally from i-40th to i-35th inch in thickness, attached to the 

 external surfaces of the shells of Orthocerata. Surface exhib- 

 iting a number of long, narrow, compressed tubercles or mon- 

 ticules, which are all occupied on their sides by the ordinary 

 corallites, though sometimes apparently more or less compact 

 at their summits. The monticules are mostly from two-thirds 

 of a line to two lines in their long diameter, with a width of 

 about half a line, and a height generally about equal to their 

 width, their distance apart being from half a line to two-thirds 

 of a line. The corallites are thin-walled, polygonal, sub-equal, 

 generally from i-iooth to i- 120th inch in diameter, and seem- 

 ingly not separated by any intercalated series of interstitial 

 tubuli, though an occasional small tube may be present. The 

 walls of the corallites are thickened as they approach the 

 surface, and the visceral chambers appear to be either open, 

 or to be intersected by occasionally developed complete 

 tabulae. 



Obs. — So far as I am aware, this species is universally para- 

 sitic upon the dead shells of Orthocerata, and often covers very 

 extensive surfaces. The most striking and characteristic fea- 

 ture in its expansions is the elongated and compressed form 

 of its monticules, which are arranged in irregular diagonal 

 lines, and always have their long axes coincident in direction 

 with the major axis of the Orthoceras upon which they grow 

 (PI. IV. fig. 2). The calices are always thin-walled and poly- 

 gonal, and there are no traces of the intercalated tubuli which 



