50 
HUGHES : mOLEBOROUGH. 
readily to denudation, and hence is rarely seen except in the beds 
of streams or in cliffs. The bands of limestone or calcareous 
sandstone generally occur quite at the top of the series. In the 
limestone seen just above the waterfall at Wharf e Mill Dam, 
Dr. Marr detected Phacops elegans Boeck. and Sars., which 
characterises a zone in the Scandinavian Silurian. Among other 
fossils found in this thin lenticular bed were Petraia elongata Phill., 
Leptoena quinquecostata McCoy, Cheirurus himucronatus Murch., 
and Encrinurus punctatus Briinn, The Spengill limestone also 
has yielded the same species, with the addition of an Illcenus, 
a small undetermined Orthis, and a lamellibranch, probably 
Cie7iodonta. 
From the district north of Ingleborough where the Grapto- 
litic Mudstone is best developed many fossils have been obtained 
which are now in the Jermyn Street Museum, but only a few 
have yet been determined and placed on record. In some beds, 
especially in the black shales, a rich graptolite fauna occurs ; 
in other beds, especially in the limestones and calcareous sand- 
stones, trilobites and brachiopods are not uncommon. The list 
of fossils collected by the Survey* from the black shales series, 
and corrected by Miss Elles, is as follows : — 
Climacograptus sp. like scalaris His. 
Diplograptus palmeus Barr. 
D. sp. ( = D. pristis of old lists). 
Monograptus lohiferus McCoy. 
M. Hisingeri Carr. ( = M. Sagittarius His.). 
M. Sedgwickii Portl. 
M. tenuis Portl. 
Rastrites peregrinus Barr. 
Now we must inquire whether there is anything in the 
character of the material of which the rocks are made up to 
explain the great difference in the thickness of the several beds 
in the Austwick section as compared with that of Spengill. In 
Spengill, the conglomerate is represented by a thin calcareous 
band, but in closely adjoining sections in the same district 
north of Ingleborough, the conglomerate is as strong as at 
Austwick, and I have already shown that there are as great 
* Mem. Geol. Survey, 98, N.E., p. 7. 
