Geological Gleanings, • 275 



reasonably draw the inference that it had been made 13,000 

 years before ?" 



6. Neio View of the Zoological relations of certain ancient corals 

 by Prof. Agassiz. The following appears in Silliman. If con- 

 firmed by farther investigation it will place nearly all our Silurian 

 corals in a different class of the Radiata, from that to which they 

 have hitherto been supposed to belong. 



" I have seen in the Tortugas something very unexpected. 

 Millepora is not an Actinoid polyp, but a genuine Hydroid, close- 

 ly allied to Hydractinia. This seems to carry the whole group 

 of Favositidae over to the Acalephs, and displays a beautiful array 

 of this class from the Silurian to this day." 



" The drawings of Professor Agassiz which have been sent to us 

 for examination, are so obviously Hydractinia? in most of their cha- 

 racters that no one can question the relation. With regard to the 

 reference of all the Favositidae (a group including Favosites, Favis- 

 tella, Pocillopora etc., as well as the minuter Melhpora, Chaetetes, 

 etc.) to the Acaleph class, direct evidence is not yet complete, as 

 the animal of the Pocillopora has not been figured by any author 

 on zoophytes.* On this point Professor Agassiz observes in a 

 subsequent letter, after observing that the Sideroporae obviously are 

 polyps : 



" There are two types of radiating lamellae, which are not 

 homologous. In true Polyps (excluding Favositidae as Hydroids), 

 the lamellae extend from the outer body wall inward, along the 

 whole height of that wall, and the transverse partitions reach only 

 from one lamella to the other, so that there is no continuity 

 between them, while the radiating lamellae are continuous from 

 top to bottom in each cell. In Milleporidae the partitions are 

 transverse and continuous across the cells and so are they in 

 Pocillopora and in all Tabulata and Riigosa, while the radiating 

 lamellae, where they exist, as in Pocillopora and many other Favo- 

 sitidae, rise from these horizontal floors and do not extend through 



" * From the specimens of the species of this genus which I procured in 

 the Pacific I never obtained a clear view of the polyps, and hence made no 

 figure. The brief description on page 523 of my Report, may be reason- 

 ably doubted until confirmed by new researches. The much larger size 

 of the cells in Pocillopora, Favosites and Favistella than in Millepora, 

 and the frequently distinct rays in these cells, are the characters I had 

 mentioned to Prof. Agassiz as suggesting a doubt as to their being 

 Acalephs, and to this what follows above relates. — J. d. d." 



