FlahelluDi, BlastotrocJius and Rhizolrochus Duncan, Jour. 

 Linn. Soc, vol. XVIII., pp. 13-15 (1885). 



Duncan divided the Turbinolidae into a number of 

 ^' alliances " of which the second is the " Flabelloida," com- 

 prising the recent genera Flabellui/i, Rhizotrochiis and 

 BlastotrocJius. These are characterised by being *' simple 

 forms with no theca and hence costae. There is no true 

 columella, but the septal edges may fuse by trabeculae and 

 fill up the axial fossa. The forms are fixed or free, with or 

 without rootlets, and generally more or less compressed." 

 As above defined the group is perfectly and morphologically 

 distinct from any other division of the Turbinolidae. 



The fossil genus Tliysanus I have not been able to examine, 

 but the three recent genera do not seem to me to present any 

 real points of difference. Blastotrochns is said to differ from 

 Flabellum by budding occurring at the sides between the 

 calicular margin and the base, the buds falling off and 

 growing. Oi Flabellum rtibriun I have examples with young 

 individuals growing similarly to the above between the 

 calicular margin and the base. They are attached principally 

 to one or other end of the calicle, but may lie on the sides as 

 well. All are completely cut off from the soft tissues of the 

 polyp, and there are no indications in any single case as to 

 whether they have been definitely budded off, or whether they 

 have been formed by the attachment of free-swimming larvae. 

 If the former be the case, a small portion of the polyp must 

 have been cut off by the advancing epitheca of the parent, as 

 there is now no trace of any connection, even the youngest 

 having indications of its own basal plate separating it from 

 the epitheca of the older corallite. In two supposed specimens 

 of the original type B. iiutn'.x from the Phillipines I can find 

 no indication of definite budding, nor of any difference 

 between the mode of attachment of the buds to that found in 

 F. rubrum. In reference to Semper it is necessary to point 

 out that he presumably supposed the corallum to*be of endo- 

 derm formation, and it is interesting to note that his 

 specimens of B. Jiutn'x, F. irregulare and F. variabile all 

 came from the same habitat, i.e., the channel of Lapinig from 

 6- 1 o fathoms. The presence of young attached forms appears 

 to me to be perhaps an accidental circumstance. In any case 

 I cannot deem it of sufficient importance to separate Blasto- 

 trocJius from Flabelliiiii. 



RJiizotrochus has hollow rootlets communicating with the 

 coelenteron of the large polyp, or with the interior of the 

 calicle of the dried corallites. I shall subsequently in F. 

 rubrum have occasion to show that in some specimens there 

 are rootlets found, precisely similar to these. Duncan states 

 as a further character that '* the columella is absent, and the 



