Mr. W. Lonsdale on the Genus Lithostrotion. 457 



(p. 619), the name Stylustrea was proposed for fossils considered 

 as allied to the one described by Parkinson, and the following 

 generic characters were given : " Columnar, lamellae exceeding 

 twelve ; columns closely aggregated, easily separated ; internal 

 structure twofold — 1st, a central area occupied by variously 

 blended lamellae or contorted lamina?, without a distinct persist- 

 ent axis ; 2nd, an outer zone, traversed by vertical, continuous, 

 bi-plated lamellae, not fasciculated ; interstices occupied by nu- 

 merous arched or vesicular laminse ; additional columns produced 

 by subdivisions of the parent column" (op. cit, p. 621). The 

 leading points of difference from Lithostrotion are a bi-areal in- 

 stead of a tri-areal composition, and a fissiparous in lieu of a 

 terminal gemmiferous mode of increase; but the subordinate 

 distinctions must not be overlooked in estimating the value of 

 the generic determinations. The agreements with Parkinson's 

 fossil consist in the basaltiform configuration and the external 

 characters of the aggregated columns, in the facility with which 

 they may be separated ; also in the plumose appearance of a lon- 

 gitudinal section*, and probably in the nature of the dissepi- 

 ments between the lamellae ; but Parkinson does not allude to 

 the composition of the centre, except that perfect terminations 

 have a projecting star ; leaving doubtful what would be the cha- 

 racters presented by a transverse section ; and the comparison is 

 still farther defective in no complete upper extremities of Sty- 

 lastrea having been seen by the author ; moreover the mode of 

 increase is neither delineated nor described in the c Organic Re- 

 mains ' (t. ii. p. 43, 44. tab. 5. figs. 3 & 6). Should the points 

 of agreement be now considered insufficient to warrant a positive 

 identification of any one of the fossils noticed in the remarks on 

 Stylastreaf with Parkinson's coral, still they are deemed enough 

 not to justify a decided generic separation. It is nevertheless 

 fully admitted, that an absolute identification of that authority's 

 coral, and consequently of those constituting Stylastrea, with 

 Lhwyd's delineation was incorrect, the available points of com- 

 parison being too few. It must also be mentioned, that the pro- 

 posed genus differs from Dr. Fleming's Lithostrotion striatum in 

 wanting the "small, solid, central axis" (Brit. Anim. p. 508). 

 Prof. M'Coy J has more recently described a new species of Sty- 



* Parkinson, ' Org. Rem.' vol. ii. p. 44 : compare the characters men- 

 tioned above with fig. 2 a of Styl. inconferta, App. A. pi. A ; also with the 

 description in p. 622, * Geol. Russia,' &c. The Bristol or Welch coral 

 noticed in pp. 6\9, 620, exhibits also in fractured vertical sections the plu- 

 mose structure ; and it is immaterial whether Parkinson alludes to the sur- 

 face of separated lamellae-plates, or to the interlamellse-dissepiments, each 

 structure when divided having a resemblance to a feather. 



t Geol. Russia, &c. vol. i. p. 619. 



X Annals and Magazine of Natural Historv, 2nd Series, vol. iii. p. 9, 

 January 1849. 



