SECONDARY AND TERTIARY FORMATIONS OF NORTH AMERICA. 167 



IDMONEA. 



Colony composed of free branches, usually anastomosing laterally. Cellules ar- 

 ranged on one face only, in transverse lines, often interrupted in the middle, and com- 

 posed of but one range of cellules to the line. Back plain or striate. 



This genus often forms large flabelliform or tortuous colonies,, arising from a common 

 base. It is distinguished from Clavituhigera, by the latter being always in a clavate 

 mass ; from Bitubigera by the cellules being in single rows, while in that genus there 

 is more than one row of cellules in each transverse series. 



I. contortilis, Lonsd., Quart. Jour. Geol. Soc., vol. 1, p. 68. 



Crisisina id ., d'Orb. Prod. Pal. Strat., vol. 2, p. 265, No. 1103. 



Idmonea id., d'Orb. Pal. Fr., vol. 5, p. 729. Id., Gabb, Catalogue Cretaceous; 

 Proc. Acad. Nat. Sci., 1859. 



Retepora, Morton, Synopsis Cretaceous, p. 79. 

 Colony composed of narrow, flattened rarely cylindrical branches, freely anastomos- 

 ing, often contorted. Cellules placed on one side, not in very regular lines, often 

 scattered indiscriminately, rarely in regular rows ; lower part of the cellules distin- 

 guishable usually by a slight undulation, upper part free exsert, cylindrical and 

 inclined slightly forwards ; sometimes there is a considerable space on a branch with- 

 out a cellule. Back of the colony flattened, when perfect, mai'ked by very coarse 

 transverse striae, curved anteriorly in the middle, only reticulated as described by 

 Lonsdale in somewhat worn specimens. When the cellules are somewhat distantly 

 placed, the upper surface also exhibits the transverse lines, though faintly. 



Locality. — Timber Creek, N. J., and near Mullica Hill. Cretaceous. In this species, 

 the cellules have a much less regular transverse arrangement than usual in the genus. 

 It has been well figured by Lonsdale. 



I. 1IAXILLARIS. 



Idmonea id., Lonsdale, Quart. Jour. Geol. Soc, 1, p. 523, 1845. 

 Crisisina id,, d'Orb. Prodr., 2. p. 397, 1847. 



" Branches forked, oval, thickness considerable ; rows of tubulate openings short, alternate, mouths in 

 contact; no central dividing ridge; tubuli very long; reverse surface semi-oval, traversed by longitudinal 

 lines, connected by minute cross lines." 



" Viewed in front, this coral resembled a Maestricht fossil, considered by Goldfuss as a young condition 

 of Idmonea gradata (Petref. Corrigenda, p. 244. Retepora distieha, p. 29, tab. 9, f. 15, a, A,) but it 

 differed essentially from mature specimens of that species, and from Goldfuss's figures, just cited, in the 

 plan of bifurcation, as well as in the great length of the tubes and the form of the branches. From La- 

 mouroux's typical species (1. triquetral, Exp. Method., p. 80, tab. 79, f. 13 — 15), and some tertiary species 

 of similar form, it was conspicuously distinguished, not merely by the rounded outline - of the reverse side, 

 but also by its great thickness." 



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