242 G. W. SHEUBSOLE ON THE VAKIOFS SPECIES OF 



find any reference to the number of pores between dissepiments 

 or in any given space. This omission is fatal to the future recogni- 

 tion of the species. Hisinger * committed the same mistake in 

 describing Betepora reticulata ; and Prof. M'Coy remarks that in 

 consequence " it is scarcely possible ever to determine Hisiuger's 

 species with certainty." Hence, from the same cause, Prof. M'Coy, 

 in compiling the Cambridge Catalogue, found it necessary to de- 

 scribe anew two of Lonsdale's species of Fenestella from Dudley. 

 There are probably in all not more than five species of Silurian 

 Fenestelloi ; and yet, with six species already described. Prof. M'Coy 

 found a difiiculty in assigning two of the ordinary types to any of 

 the then described species. The two species which, in consequence, 

 Prof. M'Coy described were Fenestella rigidula and Fenestella patula ; 

 the latter is only the young growth of one of the species. The type 

 in the Woodwardian Museum is not sufficiently well preserved to say 

 which of the several species. So it comes to this, that of the eight 

 species of Fenestellce described by Lonsdale and Prof. M'Coy, virtu- 

 ally only one species remains which is fully and accurately de- 

 scribed so as to be recognized from the text, viz. Fenestella rigidula, 

 M'Coy. 



To one familiar with the appearance of the Carboniferous Fenestel- 

 lidae, with the wonderful order and regularity of their calcareous net- 

 work, the first sight of Lonsdale's figures of the Silurian Penestellidae 

 is puzzling, to say the least of it. Apparently they form a strange con- 

 trast to them in outward form — cells visible only in the upper part of 

 the polyzoarium, carina enlarged, smoothed and rounded, interstices 

 abnormally thickened, and dissepiments placed at all angles. One 

 half of Lonsdale's drawings of Fenestellce present these anomalous 

 forms of growth. The question naturally arose. Have we here true 

 Fenestella-growth. ? A careful examination of the various reputed 

 species furnished the answer. The explanation of these peculiarities 

 is that the conical base of several species of Fenestella is the subject 

 of an abundant incrusting growth, which, in most cases, follows 

 exactly the line of the insterstice, which it conceals, as well as the 

 cell-aperture, at the same time not otherwise interfering with the 

 general outline of the Fenestella. Unfortunately portions so covered 

 over have become typical Fenestella., and as such appear in Lonsdale's 

 drawings. Nor do I find any caution respecting this abnormal 

 growth. Silence on this head leads me to suspect that the true 

 nature of the growth was not detected, and, more, that it was posi- 

 tively regarded as part of the Fenestella. Indeed there is no doubt 

 on this point — that Lonsdale was misled by the incrustation, which 

 he distinctly notices and would regard as an indication of maturity 

 on the part of the polyzoon ; for when describing the specific cha- 

 racters of the genus, he says : — " In well-preserved specimens of the 

 base of apparently old corals the pores or foramina on the side of 

 one branch have united by growth to those on the side of the ad- 

 joining branch, and constitute solid bars, either stretching trans- 

 versely and simply across the intervals, or uniting obliquely, three and 

 ^ Brit. Pal. Poss. p. 48. 



