66 Mr. H. N. Moseley on the [Nov. 25, 



number, with the membranous mesenteries. In Stylaster and Cryptohelia, 

 the calcareous septa are obviously formed as infoldings of the margin of 

 the calicles. Here the septa are between, instead of opposite to the 

 tentacles ; and membranous mesenteries appear to be absent, or at all 

 events rudimentary only. In the Favositidse the septa seem to have been 

 no more perfect than they are in Heliopora, and to have been most 

 variable in number, but often twelve, as also in Heliopora. M.-Edwards 

 describes from 10 to 12 septa in Favosites gothlandica. In Michelinia 

 favosa 30 to 40 subequal septal striao are to be made out at the upper 

 margin of the wall of the calicle. I cannot refer to specimens ; but it 

 seems not unlikely that the S3pta in the Favositidae were pseudo-septa as 

 in Heliopora, and that these coralla were formed by Alcyonarians, the per- 

 forations in the walls having transmitted transverse canals like those of 

 Heliopora and Sareophyton, and the coralla being free of tabular ccenenchym, 

 because none of the polyps were aborted as in Heliopora. Some Favosi- 

 tidae seem to have formed a compound colony, consisting of polyps and 

 zooids, as Favosites Forbesii, where a few large cells are seen set amongst 

 numerous surrounding small ones. Heliolites seems to a certain extent 

 to form a transition stage between a condition such as that in Favosites 

 Forbesii and the condition in Heliopora ; for in Heliolites, the more ancient 

 form, the ccenenchymal tubes are regularly hexagonal, and apparently 

 much more nearly equal in breadth to the calicles than in Heliopora. In 

 the growing points of Heliopora the hard parts are made up of a series 

 of open, often hexagonal tubes, and resemble Favosites in their surface 

 aspect. In Heliopora the transverse canals pass over notches in the 

 summits of the walls of the coenenchymal tubes and calicles, in order to 

 place these cavities in communication with one another. In Favosites the 

 calcareous tissue surrounded the transverse canals, and the perforations 

 in the walls of the calicles were thus produced. 



If Favosites was an Alcyonarian, Chwtetes was of course also of that 

 group. The genus Alveolites amongst the Favositidae is peculiar for the 

 possession of three tooth-like prominences as the only representatives 

 of septa. One tooth, well developed, is situate inside the calicle ; on 

 that side of each calicle which lies externally in the colony, and opposed 

 to this on the tip of the calicle next the interior of the colony, are a 

 pair of rudimentary teeth. This arrangement reminds us at once of 

 the distinction of dorsal and ventral mesenterial interspaces in Alcyo- 

 narians, and the direction of all the "Dorsalfacher" in Sarcophyton and 

 Heliopora towards the central axis of the colony. In Alveolites the two 

 teeth seem to correspond to the " Dorsalfach," and the single one to the 

 " Ventralfach," the two teeth having occupied the space devoid of retractor 

 muscles. Kolliker describes a series of teeth as existing at the margin 

 of the calicle in Menilla, which follow a constant law in their relation 

 to the septa. "When only one tooth is present it is opposite the " Dorsal- 

 fach ; " when three, one is opposite the " Dorsalfach," and the two others 



