211 
A NEW SPECIES OF UNIO FROM THE YORKSHIRE 
ESTUARINE SERIES; WITH NOTES ON OTHER 
FORMS. 
J. WILFRID JACKSON, F.G.S., 
Manchester Museum. 
(PLATE XIV.). 
WHILST my paper on Unio distortus, etc., from the Upper 
Estuarine Beds of Gristhorpe, Yorks.,* was being published, 
I received from Prof. P. F. Kendall a number of interesting 
fossil Unios, obtained from a well-defined horizon in the Lower 
Estuarine Series of Saltwick, near Whitby. The first specimen 
was found by Mr. J. W. Stather, F.G.S., in a fallen block of 
stone, but on a subsequent visit Prof. Kendall discovered the 
actual bed in which the shells occur, and several examples 
were obtained. 
On the kind invitation of Prof. Kendall I joined his geo- 
logical expedition to the Yorkshire Coast at Easter, and spent 
some time with him in examining the various exposures of 
Estuarine strata along the coast. We collected a large series 
of Unios from the Saltwick exposure, as well as others from two 
other points, Brow Alum Quarry and Haiburn Wyke, further 
south. 
The Unio-bed at Saltwick lies about 27 feet above the 
Dogger, and the shells themselves appear to be confined to a 
band of shaly material, 6 or 7 inches in thickness, underlying 
a bed of sandstone. By far the greater number of examples 
were found on their sides, with both valves closed ; others had 
the valves wide apart, but still adherent along the hinge-line. 
Only one example was seen in a vertical position, and this 
was enclosed in an ironstone nodule. The majority of the 
specimens collected were in the form of casts. 
With the possible exception of an obscure form from the 
Lower Estuarine beds, near Peak, which will be referred to 
later, the Saltwick Unios appear to be the earliest authentic 
specimens of the genus in the British Isles. Another interesting 
and important feature is that some of the better preserved 
examples possess traces of umbonal sculpture. 
As the form appears to be quite new, I have much pleasure 
in associating with it the name of Prof. Kendall as a slight 
appreciation of the excellent work he has done in Yorkshire 
and elsewhere. 
With reference to the obscure form from near Peak, the 
material at my disposal is unfortunately not very satisfactory. 
The first example was found some years ago by the Rev. 
B. C. Constable, of Stockport, in the Brow Alum quarry, on 
* ‘Naturalist,’ Feb.-Mar., 1911, pp. 104-107, 119-122, pl. 1X. and x. 
Igti Tuner. 
