STROMATOPORA BEUTHI1. 185 



general reticulation, the latter having all the characters observable in the other 

 species of Stromatopora. In thin tangential sections (Plate V, fig. 12; Plate 

 XXIII, figs. 10 and 12 ; and woodcut, Fig. 21, a and o) the cut ends of the radial 

 pillars appear as more or less distinct rounded areas in the general coenosteal 

 network, frotn which they are usually distinguished by their greater density and 

 darker colour. In some instances, as in Plate XXIII, fig. 12, they appear as light 

 spaces, with a dark central dot representing the axial canals of the pillars. In 

 parts of thin tangential sections — corresponding probably with places where the 

 plane of the section traverses an interlaminar space — it is also not unusual 

 to find that the reticulated character of the skeleton is lost, and we simply see the 

 isolated rounded or oval ends of the transversely divided radial pillars. In such 

 cases, as shown in Fig. 21, a (in the lower part of the figure), the radial pillars are 

 seen to consist of an external sheath of porous tissue surrounding a central more 

 compact core. On the other hand, the horizontal or oblique connecting-processes 

 which join the radial pillars with one another, and which constitute the " concen- 

 tric laminae," are wholly composed of porous tissue, and have no central core. In 

 thin vertical sections (Plate XXIII, fig. 11) the radial pillars are at once 

 recognisable, but their central axes are usually but indistinctly seen. In some 

 cases, however, as in Fig. 21, b, the dark central axes of the pillars can be clearly 

 made out. 



8. Beuthii, Barg., commonly occurs in the " Caunopora-state " (Plate XXIII, 

 fig. 13; and Plate XXIV, fig. 1), in which condition it is with difficulty separable 

 from 8. Hwpschii, the distinctive character of the persistent radial pillars being 

 much obscured or wholly lost. 



I am not acquainted with any well-marked varietal forms of 8. Beuthii. The 

 species with which 8. Beuthii is most nearly allied is S. Hwpschii, Barg., and the 

 chief points of distinction between the two have been already pointed out in 

 speaking of the latter form. In a general way, and in well-preserved examples, 

 S. Beuthii is distinguished from 8. Hwpschii by the more clear separation of the 

 radial pillars from the general coenosteal reticulation, and the less loose and open 

 character of this latter ; while the astrorhizas are incompletely developed or may 

 be absent, and the zooidal tubes are more closely tabulate. Badly preserved 

 specimens, or " Caunoporised " examples of 8. Beuthii are, however, hardly to be 

 distinguished with certainty from those of 8. Hwpschii. There is no species of 

 Stromatopora, except the above, with which 8. Beuthii could be easily confounded. 



Distribution. — 8. Beuthii appears to be wholly confined to the Middle Devonian 

 Rocks, occurring in deposits of this age both in Britain and on the Continent of 

 Europe. In Devonshire it is commonly found in the limestones of Pit-Park 

 Quarry, Dartington, and of Bishopsteignton, most examples being " Cauno- 

 porised." It also occurs with moderate frequency in the Devonian pebbles of the 



