OL 
2 
THE CRETACEOUS LAMELLIBRANCHIA 
OF YORKSHIRE. — 
CHARLES P. CHATWIN, F.R.M.S. 
WHEN Mr. Henry Woods essayed to write a monograph of 
the Cretaceous Lamellibranchia the nomenclature of that 
group was extremely unsatisfactory. Only three. families, 
the Trigoniide, the Nuculanide, and the Nuculide had received 
detailed attention ; and the literature of the whole class was 
extensive, and scattered through numerous journals and separ- 
ate publications. The first part of the monograph was pub- 
lished by the Paleontographical Society in 1899, and since 
then one part has appeared every year, and the work is now 
complete in two volumes. 
Lamellibranchs from all the English Cretaceous rocks 
have been dealt with in the monograph, and the present seems 
a suitable opportunity of recording in general terms the 
results of Mr. Woods’ work so far as the species from Yorkshire 
are concerned. The following notes therefore are compiled 
from. the monograph, in which we believe most authentic 
records to be included ; and they are intended chiefly for the 
use of local collectors. 
The Nuculas were studied by Starkie Gardner in 1884, 
but have been subjected to further revision in the present 
work. Thus to the genus Nuculana are referred Forbes’s 
Nucula spathulata (which occurs as doubtful casts), Phillips’s 
Nucula subrecurva, and Gardner’s Leda seeleyi. The species 
described by Orbigny as Nucula scapha, and considered by 
Gardner as Leda, is now to be called Nuculana [? Yoldia| 
scapha, and Nuculana speetonensis, Woods, is a new species, 
probably the same as that denoted by the manuscript name 
Nucula equilateralis of Bean (not of F. A. Roemer). Among 
the Nuculide, N. ovata, Phillips (not Mantell), has been found 
to be synonymous with N. planata, Deshayes, which name 
must now be used; and a new species -N. lamplughi, Woods, 
has been founded for a form much like N. flanata. All the 
foregoing species come from the Speeton Clay (Lower Cre- 
taceous) of Speeton. The name of the form that occurs in 
the minimus-marls of the same locality, Nucula pectinata, 
J. Sowerby, remains unchanged. 
The specimen that occurs in the brunsvicensis-zone at 
Speeton, which Phillips, in his first edition of the ‘ Geology of 
Yorkshire,’ called Cucull@a, and in the third edition Cucullea 
securis, can now be referred to as Grammatodon securis (Ley- 
merie). The genus Plicatula is represented by two species, 
P. placunca, Phillips, a doubtful determination from the Lower 
Cretaceous of Speeton, and P. inflata, J. de C. Sowerby, from 
the Chalk Marl and subglobosus-zone of Speeton. The latter 
1913 May I. 
