Mr. W. Lonsdale on the Genus Lithostrotion. 469 



Parkinson's Lithostrotion and in the Kendal fossil will possibly 

 be regarded by most observers as an axis, in which case, as re- 

 spects at least the latter, the zone under consideration will not 

 exist. Regarding Cyath. basaltiforme no opinion can be hazarded 

 whether it has a representative of this intermediate area ; but in 

 Stylastrea, if the transverse lamina? be considered an equivalent 

 structure, then there is no axis. One of Mr. Dana's delineations 

 of Columnaria indicates on each side of the central composition a 

 narrow band (op. cit. pi. 26. fig. 9 b), which however becomes 

 evanescent in the upper part of the figure ; and his other vertical 

 section (fig. 10) gives no analogous zone ; while, according to the 

 following extract from the generic description, he possibly did 

 not consider that an intermediate band exists— *" Corallum 

 having the cells radiate, the middle within consisting of oblique 

 septa and cellules converging upwards into an axis ; texture ex- 

 terior to the middle portion, cellular" (p. S63). Nemaphyllum, 

 on the contrary, has an intermediate zone, or " a sharply defined 

 cylinder of very minutely vesicular arehed plates, the rows 

 directed from the axis obliquely downwards and outwards ; " and 

 the illustrative woodcut expresses very nearly what is sometimes 

 visible in the equivalent portion of Lithodendra. In that genus 

 however, so far as is known, the zone is not (< a sharply defined 

 cylinder/ - ' and the circle occasionally shown in transversely cut 

 corallites is an intersected upward-inclined plate ; and not part of 

 a continuous, vertical lamina as in Prof. M'Coy's figure (op. cit. 

 p. 15). This will most probably be regarded by many palaeon- 

 tologists as an unimportant distinction, nor is it advanced as a 

 valid generic difference by itself; but when taken in conjunction 

 with the mode of reproduction, and the inseparable union of the 

 stems, it forms one of a series of dissimilarities. 



With reference to the agreements or otherwise in this portion 

 of the Lithostrotion of the 'Archives/ it appears, that in the 

 branched fossils referable to Mr. Phillips's Lithodendra, there is 

 a large intermediate area of somewhat variable character, but 

 essentially composed of curved laminse inclined upwards and 

 centrally — that in Lhwyd's fossil, Dr. Fleming's Lithostr. stria- 

 turn and Cyath. basaltiforme, there is no authority for assuming 

 its existence — that in Parkinson's Lithostrotion, also in the 

 Kendal coral, and possibly in Mr. Dana's Columnaria, it is want- 

 ing, if the complicated central lamina; be regarded as an axis — 

 and that in Stylastrea provided the transverse plates be an equi- 

 valent, there is no axis; while in Nemaphyllum an analogous zone 

 is present, but- in conjunction with other peculiar characters. 

 Hence it may be inferred, that there is no prevalent agreement 

 in this particular between branched and massive or asteriform 

 specie*; and even in Lhwyd's Lithostrotion or Dr. Fleming's L, 



