262 Proceedings of the Royal Physical Society. 
lateral angles much developed, lower margin semicircular 
and forming a sinus at each side where it joins the lateral 
angles; cicatricules three, the lateral lunate, the central 
punctiform. Above the leaf-scar the ribs are ornamented 
with fine lines somewhat irregularly placed, but soon 
assuming a general direction parallel to the ribs. From the 
sinus at the top of the leaf-scar two lines extend upwards 
and outwards for a short distance. 
I have named this Sigillaria after its discoverer, Dr John 
Young, of the Hunterian Museum, Glasgow, who found it in 
1864 in a bed of shale passed through in sinking a pit to 
reach the upper Possil blackband ironstone and associated 
coal at Robroystone, near Glasgow. 
Its nearest ally appears to be Szgillaria contracta, Brongt.,' 
but it is easily distinguished from this species by the form 
and position of the leaf-scars, as well as by the ornamentation 
of the ribs. 
In Sigillaria contracta, Brongt., the leaf-scars are placed 
on the contracted portions of the ribs, while in Sigillaria 
Youngiana they are on the expanded areas. The form of 
the leaf-scar in the former is pyriform, with feebly developed 
lateral angles; in Sig. Youngiana it is emarginate, broader 
than long, and the lateral angles are developed to an unusual 
extent. The ornamentation of the ribs is also different. The 
two species are very distinct, and the only point they have in 
common is the alternately contracted and expanded ribs. 
Sigillaria Youngiana, of which a single specimen has been 
found, is the only example of a ribbed Sigillaria I have yet 
seen from the Lower Carboniferous Rocks of Britain, and this 
circumstance adds considerable interest to the fossil. 
The specimen has been placed in the collection of the 
Hunterian Museum of the University, Glasgow, by Dr John 
Young, and my thanks are due to him for his kind permission 
to figure and describe it. 
Horizon.—Carboniferous Limestone Series; Possil Iron- 
stone Group. | 
Locality—Robroystone, about four miles north-east of 
Glasgow, Lanarkshire. 
1 Hist. d. végét. foss., p. 459, pl. exlvii., fig. 2, 
