LONSDALE ON MIOCENE CORALS FROM N. AMERICA. 499 



Steeple Ashton * (England), and believed to be referable to the 

 Thamnastrea of Lesauvage. In that fossil, however, there is no 

 columnar structure at any period of growth, but a perfect blending 

 of lamellae ; and there is no thickening layer. In specimens of 

 Porites pyriformis obtained by Mr. Austen from the Devonian 

 limestones of England, changes equally great with those exhibited 

 by Columnaria ? sexradiata have been noticed j" ; and the lamellae- 

 tubes of Heliopora cozrulea (De Blainville) are at one period 

 totally obliterated by an extension and union of the lamellae : 

 again, in Pocillopora acuta (Lamarck) the polype cavities, always 

 shallow, are in lower portions of a specimen sometimes perfectly 

 filled up, and occasionally difficult to detect ; while in Oculina 

 virginea, the tubes cease after a time to be prolonged, though 

 the intermediate spaces continue to thicken, and finally to 

 extend over the mouths of the tubes : lastly, another case of ob- 

 literation, unattended, as in the Oculina, by any marked changes in 

 the structure of the part occupied by the body of the polype, 

 has been noticed in a specimen of Gemmipora crater ? (De 

 BL), in which the oldest of the projecting stars were com- 

 pletely buried under a thickened extension of the intermediate 

 reticulated structure. These changes, partly noticed on former 

 occasions, are mentioned, because they are believed to be of great 

 importance in generic, and under modified conditions in specific 

 determinations, and because they do not appear to have claimed 

 sufficient attention. 



As respects the reproductive process, it is necessary to premise 

 that not a single indication was observed of a subdivision in a ter- 

 minal star. Cases of interpolated small or young columns were 

 not numerous on the surface of the large flat or conical specimens, 

 on account, it was inferred, of the sudden divergence and restricted 

 growth of the columns having produced feAV interspaces ; but in 

 conical or lobed specimens, which implied continued growth, young 

 stars were noticed, irregularly crowded between others of greater 

 dimensions, with more or less well-defined lines of separation or 

 partition ; and along the centre of fractional sections similar proofs 

 of interpolation were exposed. 



Localities. — Evergreen, James's River, Petersburg ? 



3. ASTREA HIRTOLAMELLATA Michelill ? 



Stars polygonal in close contact, unequal ; lamella? numerous, alternately 

 broad and very narrow, sides papillated, edges rugged ; centre union of lamella? ; 

 terminal cup deep, edges of lamellae considerably curved ; boundary between 

 the stars sharp, rugged, no blending of lamellae. 



Astrea hirtolamellata Michelin ? Iconographie Zoophytolo- 

 gique, p. 162. pi. 44. f. 5. 1845. (Parnes, Grignon, &c.) 



* See Mr. Lyell's Elements of Geology, 2d edit. ii. p. 43. fig. 239. ; also 

 the Astrea favosio'ides of Smith's Strata Identified, Coralline Oolite, fig. I. ; 

 and Phillips's Geol. Yorkshire, part i. p. 126. pi. 3. fig. 7. Likewise consult 

 Thamnastrea Lamourouxii, Michelin's Icon. Zoophytologique, p. 109. pi. 25. 

 ng. 3. 

 f Trans. Geol. Soc. of London, 2nd ser. vol. v. descrip. pi. 58. fig. 4. 



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