64 PAUEONTOLOOy OF rUEW-YOKK. 



CORALS OF THE TRENTON LIMESTONE. 

 Plates XXIII. to XXVI. 



The corals of the Trenton limestone are limited to a moderate number of species, and a 

 few only of these are abundant ; but one species, the Ch^tetes, in some of its varied forms, 

 abounds in nearly all localities of the rock. These species, of which there about eighteen, 

 are referable to no less than twelve distinct genera. The Chtetetes Lycoperdon, in hemi- 

 spheric forms, often abounds in certain layers, to the almost entire exclusion of any other 

 fossil ; while the slender and branched varieties of the same species are foimd in other 

 situations, covering the entire surface of strata for many yards in extent. These corals rarely 

 attain to massive dimensions, though we sometimes meet with irregular forms weighing 

 ten or twelve pounds. This species is far more abundant than any other, and, in some of 

 its protean forms, is every where met with in the Trenton limestone, being much more 

 numerous than all the other species together. 



During the entire deposition of this rock, the condition of the ocean does not appear to 

 have been favorable to the continued growth of corals, since no massive species are found 

 in it. This is probably owing to the constant intermingling of shaly matter during the time, 

 which interfered with the growth of these animals ; for there seems no other sufficient 

 reason, since such large masses of the Columnaria are found in the thin layer of Black- 

 river limestone below this rock. The western extension of this formation shows, during the 

 same period, the existence of immense numbers of corals, none of which attain to large 

 dimensions, though in their present condition they form a considerable proportion of some 

 of the strata. 



101. 2. CH^TETES LYCOPERDON. 



Pt. XXIIl. Figs. 1, la,b,c, d, e,/, ^. *,»,&. 2, 2 a, 3 ; and Pi,. XXIV. Figs. 1 a, b, e, d, «,/, g, h, i, k, m, n, o. 



Favontet Lycoperdon. Say. 



Fatotilet lycopoditet. Vajtoxem, Geol. Report, pag. 46, fig. 3. Emmoits, Geol. Report, pag. 3S9, fig. 3. 

 Calamopora fibrosa [ I ] Golj>fu88, 1826, Petrefacta, pp. 82, 21.'5, tab. xxviii. figs. 3 & 4 ; tab. xxiv. fig. 9. 

 Favositet fibrosa? Goldfuss, 1833, Petref. corrigenda, p. 215. 



Compare Oueteta petropoHlantu, Lonsdale ; Favositea petropolitana. Pander. Murchison & VEBNXtnL, 

 Geology of Russia and the Ural Mountains, pag. 506, pi. A. fig. 10. 



Coral polymorphous, composed of closely aggregated tubes or columns, which diverge 

 gradually from a broad base forming hcmisplicrical masses, or from an imaginary axis 

 producing conical or ramose forms ; tubes minute, fibre-like, traversed by diaphragms ; 

 no connecting pores ; increase of the coral by subdivisions of the parent tube, or by the 

 successive addition of lateral or marginal tubes ; Exterior envelope submembranous. 



This abundant coral appears in hemispherical, conical, nearly globular and ramose forms. 

 Its most usual form is the hemispheric or puffball-shape, from which it received its name 



