GENUS LABECHIA. 81 



form upon their upper convex surfaces. The external surface usually exhibits 

 larger or smaller tubercles, representing the upper ends of the radial pillars. No 

 astrorhizaa are present. A basal epitheca is often present. No definitely circum- 

 scribed zooidal tubes appear to exist. The skeletal tissue is mostly apparently 

 compact or granular; but its minute structure has at present been imperfectly 

 investigated. [The radial pillars of Labechia conferta appear to have a peculiar 

 cribriform structure, apart from their possession of axial canals.] 



It would be easy to give a satisfactory definition of this family, if we were to 

 include in it only the various species of Labechia, E. and H. It is, however, 

 impossible in the present state of our knowledge to frame a sufficient diagnosis of the 

 family, if we include in it, as we seemingly must do, not only the singular Rosenella 

 dentata, Rosen, sp., and its allies, but also the still more aberrant types included by 

 Billings under the name of Beatricea. As a merely provisional arrangement, we 

 may also place in this family the very incompletely known genus Dictyostroma, 

 Nich. 



Genus Labechia, Edwards and Haime. 



(' Polyp. Foss. des Terr. Paleoz.,' p. 279, 1851.) 



The skeleton in this genus is laminar or massive, usually furnished with a 

 concentrically wrinkled basal epitheca (Plate III, fig. 7), and attached by a small 

 peduncle, and not genuinely encrusting, though often involving foreign bodies in 

 its growth. Very young examples (Plate III, figs. 9 — 11) consist of a flattened 

 circular basal epitheca supporting a single layer of blunt tubercles on the upper 

 surface. Adult examples have these tubercles developed into stout radial pillars, 

 which are continued through the thickness of the coenosteum without a break, and 

 terminate on the upper surface in blunt and apparently imperforate tubercles. 

 The radial pillars contain a distinct axial canal, but they would seem to be solid at 

 their apices. They run parallel to one another, and are united by curved or straight 

 calcareous plates which form a series of large-sized vesicles, filling up all the inter- 

 spaces between the pillars. Owing to the entirely irregular development of these 

 vesicles, the coenosteum shows no tendency to split concentrically, as is observed 

 in the normal Stromatoporoids, and there are no definite " concentric laminae." 



The skeleton in the genus Labechia, B. and H., has in the main a resemblance 

 to that of Actino stroma, Nich., but it differs from this in the great size of the 

 radial pillars, and in the fact that the horizontal processes which are developed 

 from these appear to have the form of convex or flat plates, instead of mere fibres, 

 while they are produced with such irregularity as not to give rise to distinct 

 " laminas." The radial pillars are undoubtedly hollow, and contain an axial canal 



