THE 



GEOLOGICAL MAGAZINE 



NEW SERIES. DECADE VI. VOL. II. 



No. X.— OCTOBER, 1915. 



ORIG-HsTAL ARTICLES. 



I. — On Labechia botunda, a new species of Stromatoporoid, 



FROM THE WeNLOCK LlMESTONE OF SHROPSHIRE. 



By Miss M. S. Johnston. 

 (PLATE' XV.) 



WHILST working at the fossils connected with our paper 

 "A Study of Ballstone and the Associated Beds in the 

 Wenlock Limestone of Shropshire ", 1 my colleague, Miss M. C. 

 Crosfield, and I became much interested in a small round form of 

 Labechia. "We did not find many specimens, about a dozen in all, 

 although we spent a considerable time in collecting, and these were 

 obtained at only three quarries, wlfich contain otherwise a prolific 

 fauna, viz. Bradley Rock and Shadwell Rock, Much Wenlock, and 

 at Knole Quarry, Presthope. The tops of these quarries are in the 

 highest beds of the Wenlock Limestone series and are of bands of 

 irregularly shaped nodules of various sizes, with shale partings and 

 of a light-brown colour (this latter fact distinguishes the beds from 

 the rest of the limestone). It is only in these upper beds that this 

 Labechia is found, but Labechia conferta, Lonsd., is found, often in great 

 numbers and size, everywhere throughout the limestone, though 

 perhaps slightly diminishing in quantity at the top. So far, I have 

 not been able satisfactorily to identify this species. Nicholson, in 

 his monograph, 1 mentions and figures a young example of L. conferta, 

 which he records as only being 2 to 3 cm. in diameter and 1 mm. in 

 thickness. This specimen agrees with mine, but I cannot believe 

 that they are young Labechia conferta, Lonsd., for several reasons — 



1. The species is only found in the highest beds, never in the 

 lower. 



2. The largest I have is 5+cm. in diameter (PI. XV, A, Pig. 1). 



3. It is always thin, about 2 mm. thick (PI. XV, A, Fig. 3, and B), 

 and never has one colony superimposed on another (PI. XV, A, Fig. 6 ; 

 a Labechia conferta is 1 cm. thick). 



4. The basal epitheca is nearly flat, not protuberant as is the 

 case in many L. conferta (PI. XV, Figs. 4, 5). 



5. The rings of growth are always circular and never irregular 

 (PL XV, A, Figs. 1, 2, and B). 



The upper surface is seldom found exposed, but where it is seen 

 it is irregularly or sometimes radially studded with minute tubercles. 



1 Proc. Geol. Assoc, vol. xxv, pt. iii, pp. 193-224, pis. xxxiii-vi, 1914. 



2 British Stromatoporoids (Pal. Soc), p. 161, pi. iii, figs. 9-11. 

 DECADE VI. — VOL. II. — NO. X. 28 



