30 PALAEONTOLOGY. 



ering, so as to expose the edges of the septa, thus presenting a distinctly 

 striated appearance ; surface^ more or less wrinkled transversely, but not very 

 strongly so ; septa from about thirty-six to forty, every alternate one of which 

 is slightly thinner than the others, and generally terminates at, or a little 

 within, the thin wall of the outer vesicular zone, while the others continue 

 straight inward, and terminate abruptly a little before reaching the middle. 

 Vertical section showing the narrow central space not occupied by the 

 septa to be crossed by transverse plates, which seem to curve downward, 

 and sometimes to divide all around the central transversely septate space, 

 so as to form a kind of narrow, undefined inner vesicular area. Out- 

 side of this, there is a well-defined, very narrow, outer, vesicular zone, sepa- 

 rated from the inner by a distinct, very thin wall, and occupied by only a 

 single series of vesicles, the dissepiments between which range obliquely 

 outward and upward. (Calices unknown.) 



Entire size of corallum unknown; diameters of corallites, from 0.16 to 

 0.20 inch; spaces between the corallites rarely greater than the diameter of 

 the latter, and generally less. 



This coral seems to present essentially the structure of the genus Diphj- 

 phyllum of Lonsdale, particularly as illustrated by Professor McCoy in his fig- 

 ures of his B. latiseptum (Brit. Pal. Foss., pi. 3 c, fig. 10.) Specifically, 

 however, it diff'ers materially from-that form in having more slender coral- 

 lites, and a much narrower, outer, vesicular zone, as well as a proportionally 

 wider middle area occupied by the broad tabulae. 



I am aware that Edwards and Haime have expressed the opinion, in 

 their valuable Monograph of the Fossil Corals (p. 446), that the specimens 

 on which Lonsdale's genus Dipliyphyllmn was founded, and those of another 

 species described by McCoy) are probably only examples of LHliostrotion, 

 in which the columella had accidentally been dissolved out during the 

 process of fossilization. If this is so, the name of the species here under 

 consideration would probably become Biplophyllum fasciculwn, as it seems 

 to present very nearly the structure of that genus as proposed by Professor 

 Hall, who, however, has since expressed doubts whether or not his genus is 

 distinct from BipJiyphyllimi of Lonsdale. 



Whatever may be the real structure of Lonsdale's typical specimens of 



