174 BRITISH STROM ATOPORO IDS. 



the species is extremely abundant, occurring in numerous localities, as, for 

 example, at Ironbridge, Dudley, Dormington, Longhope, and Much Wenlock. 

 It is also a common form in the "Wenlock Limestone of Gotland, though most of 

 the specimens I have seen from this region are more or less altered by crystallisa- 

 tion. In Esthonia, in the Upper Oesel formation, it occurs plentifully, specimens 

 being abundant at Lode (near Arensburg), Kaugatoma-pank, Kattri-pank, or 

 Hoheneichen, all in Oesel. It also occurs in the Drift in Northern Germany. If 

 I am right in regarding Ccenostroma galtense, Dawson, and S. constellatum, 

 Spencer, as identical with 8. typica, Rosen, then the species occurs in the Silurian 

 Rocks of North America as well as in Europe. 



3. Stromatopora Carteri, n. sp. PL I, figs. 6 and 7 ; and PI. XXIII, figs. 1 — 3. 



The ccenosteum in this species is of considerable size, massive, irregular in 

 shape, and composed of gently undulated or curved latilaminas (Plate XXIII, 

 fig. 1), which vary from 2 to 4 or 5 mm. in thickness in their central portion. 

 The under surface and mode of attachment are not known, but the upper surface 

 is without distinct eminences or " mamelons," and shows simply an irregular 

 vermiculate tuberculatum. Astrorhizse are not developed in any recognisable 

 form. 



As regards internal structure, the skeleton-fibre is about ^ mm. in diameter, 

 and is coarsely porous (Plate I, figs. 6 and 7). Vertical sections (Plate XXIII, 

 fig. 2) show that each latilamina is composed of very distinctly developed radial 

 pillars, which are separated from one another by equally distinct zooidal tubes, 

 and which really run continuously from the bottom to the top of each latilamina ; 

 though they appear to be more or less broken up, if — as in the example figured — 

 the plane of the section is slightly oblique. About seven radial pillars, with their 

 intervening zooidal tubes, occupy a space of 2 mm., measured transversely. The 

 zooidal tubes are furnished with a moderate number of well-developed transverse 

 partitions or " tabulae." The radial pillars are connected at varying intervals by 

 irregular horizontal or oblique processes, but these do not give rise to distinct 

 " concentric laminae," and the skeleton thus forms a loose and open reticulation, 

 in which the vertical elements are far more conspicuous than the horizontal. As 

 a result of this, tangential sections (Plate XXIII, fig. 3) show the cut ends of the 

 radial pillars, either as separate structures, or, more usually, as united by the 

 irregular horizontal processes above spoken of in such a way as to give rise to 

 vermiculate and sinuous rows, which inosculate with one another and form a 

 lax network. 



Obs. — The specimens upon which I have founded this species, though mode- 



