470 Mr. W. Lonsdale on the Genus Lithostrotion. 



striatum, the very existence of the most prominent part of Litho- 

 dendra remains to be ascertained. 



The outer zone is simply stated in the ' Archives ' to consist 

 of "^des traverses vesiculaires" (Gen. Char. p. 432) ; and Mr. Phil- 

 lips^s figures \2, 13, 15, 16 and 20, also 17 and 19, exhibit a 

 narrow band similarly constituted, though each delineation varies 

 somewhat in character. A specimen which afforded many trans- 

 verse sections of a species probably referable to L. fasciculatum 

 (Phill. pi. 2. figs. 16, 17) gave two conditions of this zone — one 

 which presented simply alternations of very broad and very nar- 

 row lamellae ; while the other had equivalent plates connected by 

 a more or less regular circle of arched plates, the narrow lamellae 

 pi'ojecting just beyond it, as in figure 16 (Phillips), or a series of 

 somewhat quadrangular cells was interposed between the wall of 

 the corallite and the circle. A polished slab thickly beset with 

 transverse and oblique intersections of apparently Lithod. sexde- 

 cimale yielded a few examples almost as regularly constructed as 

 in figures 12 and 13 (Phillips) — the characters being either a, 

 simple series of broad lamelJEc united by a circle of diaphragms 

 and forming a single circle of cells (fig. 12), or analogous cells 

 indented by rudimentary lamellae (fig. 13). The sections gave, 

 however, very generally much less uniformity; and in oblique 

 cuttings there was necessarily a total want of symmetry. The 

 outer zone of the fossil which was believed to be Lithod. irre- 

 gulare (Phill. figs. 14 and 15) had a similar composition, or a 

 row of small cells adjacent to the boundary-wall, and a large 

 inner series as shown in figure 15 just quoted; but in the speci- 

 mens examined, care was necessary to reduce the exhibited struc- 

 tures to that type ; and the arrangement was even then detect- 

 able only in the most directly transverse sections. The breadth 

 of the zone was limited in all cases, but greatest in L. irregulare ; 

 and in some vertically cut corallites it was occasionally almost 

 wanting. No opinion can be formed respecting the existence of a 

 similar outer area in Lhwyd's fossil or in Dr. Eleming^s Lithostr. 

 striatum. Parkinson says that transverse sections of his coral 

 resemble a spider's web, displaying " numerous and exceedingly 

 slender longitudinal lamellae corresponding with the external 

 striae,'' and " disposed perpendicularly from the circumference to 

 the centre in a stellated form;" also "proportionally numerous and 

 equally delicate lamellae perpendicularly disposed nearly in con- 

 centric circles" (Org. Rem. ii. p. 44) ; and his figure 3 (pi. 5) 

 displays exactly such a structure. No data however are given 

 whereby the interior of the corallites can be separated into areas, 

 except that the prominent star may constitute one, and all exterior 

 to it another. Mr. Sharpe's Kendal fossil conjecturally associated 

 with Parkinson's coral had also numerous delicate lamellae, half 



