GENUS BEATRICEA. 87 



One of the great difficulties connected with the study of Beatrlcea arises from 

 its apparently uniformly poor state of preservation. The skeletal tissue seems to 

 have been very delicate and apparently very readily dissolved ; hence the central 

 portions of the ccenosteum are very commonly more or less largely replaced by 

 calcite, while larger or smaller tracts throughout the skeleton are either similarly 

 replaced, or are completely broken up. Moreover, even where the actual structure 

 of the skeleton has been retained, it seems to have undergone some secondary 

 change which has rendered its interpretation exceedingly difficult, certain parts of 

 all the sections which I have prepared always showing a cloudy and granular 

 aspect by which the minute details are hopelessly obscured. 



The two conspicuous features in the skeleton of Beatrlcea, as displayed by 

 transverse or longitudinal sections of the cylindical coenosteum (PL VIII, figs. 2 

 and 3), are the axial tube and the peripheral vesicular tissue. The axial tube is a 

 longitudinal canal, generally 5 — 6 mm. in diameter, running the entire length of 

 the cylindrical ccenosteum. It has no definite walls, but is formed by the super- 

 position of a series of deeply convex vesicles of large size, the convexities of which 

 are all turned in one direction (PL VIII, fig. 3). Whether the convexities of these 

 curved tabula? point to the distal or to the proximal end of the ccenosteum I am 

 unable to say, but I incline to think that they point to the former. 



The remainder of the skeleton is formed by a thick sheath of vesicular tissue, 

 formed of lenticular calcareous cells, arranged in successive concentric zones round 

 the axial canal, and having a general long diameter of from 1 to 3 mm., their con- 

 vexities being uniformly turned towards the exterior of the cylinder. The general 

 character of the vesicles, superficially at any rate, is very similar to that of the 

 cellular tissue of CystiphyUum ; and, if we take the axial canal as representing a 

 central tabulate area, there would be considerable ground for regarding Beatrlcea 

 as an ally of the Cystiphylloid Corals. 



The structure of the vesicles is, however, not so simple as might at first sight 

 appear. In all thin sections, in whatever direction they may be taken, the 

 interior of the vesicles is more or less extensively occupied by ill-defined granular 

 calcareous matter, which, beyond doubt, belongs to the skeleton of the fossil. 

 Sometimes the entire cavity of the vesicle is filled with this granular tissue, but 

 more often the vesicle is only lined with it, the lining being often confined to the 

 convex margin of the vesicle, the rest of the space being filled up with cal- 

 cite. That this granular tissue is properly part of the ccenosteum, and not a mere 

 product of mineralisation, is shown by two facts. In the first place, in certain 

 specimens, towards the exterior of the cylinder, the walls of the vesicles disappear 

 to a larger or smaller extent, and then the granular matter which lined them forms 

 a series of concentric lamina?, resembling the " lamina? " of an ordinary Stromato- 

 poroid. In the second place, most specimens have this granular material in the 



