1848.] LONSDALE ON TOSSIL ZOOPHYTES. 93 



stems, and between them are interlaced fibres with small pits or 

 foramina. The reverse side of the same portion is strongly though 

 irregularly ribbed, and there are considerable interspaces traversed 

 also by fibres, often disposed obliquely as respects the area, but ver- 

 tically with reference to the growth of the branch. The intervals 

 have likewise distinct pores. In the specimen immediately under 

 consideration the whole surface of the stems began to be modified 

 about three lines from the upper extremity by a fibrous thickening, 

 which gradually increased downwards, widening also the branches, 

 and filling up more or less completely the spaces between the pro- 

 jecting openings, and finally obliterating, in very aged conditions, 

 the latter, rendering both surfaces nearly uniform in character. The 

 lateral shoots and their offsets preserved, on the contrary, an equal 

 breadth from their point of divergence nearly to their extremity, 

 even in a case nine lines in length, and on whatever part of a speci- 

 men they were situated. These shoots were apparently the young 

 branches of M. Milne-Edwards* ; but the long-continued, if not 

 permanent diiferences between them and the main stems, are not 

 apparently alluded to by him. The shoots with their offsets had a 

 very hispid appearance. M. Edwards says, that in young branches, 

 " la portion terminale des cellules est tres saillante, et I'espece inter- 

 mediaire rugueuse " {op. cit. p. 44, desc. fig. la). On coating one 

 with ink, and examining it under a Codrington lens, the intervals 

 were clearly traversed by fine ribs, sometimes parallel, but often con- 

 verged towards each other, forming a lozenge-shaped figure around 

 the apertures. These areas were indented or foraminated similarly 

 to those of the main stems, but no fibres were detected, nor decided 

 thickening, though the shoot was five lines in extent. The reverse 

 side was occupied by broad granulated ribs with fine intermediate 

 furrowsf, but not a vestige of a fibrous structure was visible through- 

 out even the nine-lines shoot. The difference between a thickened 

 and non-thickened surface is well-expressed in M. Edwards's figure 

 1 a (letters u and b) ; but it is most conspicuous in specimens them- 

 selves, and in those portions where the shoot issues from the side of 

 an aged stem, not the least encroachment of the fibrous structure 

 being visible upon the former. It is of little importance in the pre- 

 sent inquiry whether the differences are permanent or not ; it is suf- 

 ficient to point out their existence mider certain conditions. In the 

 lower greensand fossil no similar distinctions exist, all branches 

 being perfectly alike ; and the thickening is not effected by longitu- 

 dinal fibres, but by local amorphous secretions. Respecting the 

 minor openings in main stems of Horn. J)^ondiculata^ fragments pur- 

 posely worn down showed that they were only foramina which 

 penetrated the general crust of the coral, and not distinct tubuli with 

 a surrounding open area. Lateral shoots prepared in the same man- 

 ner also proved that the surface minor openings were pores in the 

 wall of the tubes. In the Isle of Wight fossil, however, the secondary 

 apertures on both sides of a branch have, within the body of the 



* Op. cit. pp. 18, 19 ; also pi, 9. fig. la, with description of figure, p. 44. 

 t Consult M. Milne-Edwards's figure 1 c, op. cit. pi. 9, and description, p. 44. 



