142 J. S. GARDNER ON BRITISH CRETACEOUS NUCULIDA. 
except in the rare case of a variety being met with departing 
abnormally from the specific type. The species are: — 
N. ovata, Mant. | NN. bivirgata, Sdy. 
N. capseeformis, Mich. N. gaultina, Gardn. 
N. albensis, d Orb. | L. Vibrayeana, d’Orb. 
N. arduennensis, var. pumila, | L. phaseolina, Mich. 
Gardn. L. Mariz, d@’ Orb. 
N. pectinata, Sdy. | L. solea, d’ Orb. 
A comparison with lists that have been published, both of the 
Cambridge and Folkestone Gault species, will show that the number 
is here rather reduced than added to. Two new species are added, 
both being exquisitely preserved and abundant little shells, whose 
ack: though most obvious, had hitherto remained unrecog- 
nized. 
Many, the majority in fact, of the Gault forms reappear, slightly 
modified, in the Blackdown Beds, with the notable exception of the 
two forms, VV. pectinata and N. bivirgata, which, we have seen, are 
equally unknown in the Neocomian. The forms J. obtusa and NV. 
empressa of the “ Ovate” are perfectly distinct from each other; and NV. 
antcquata can be immediately distinguished by the toothing along its 
margins ; nor is there any fear that the two species of Leda can be 
confused ; for the one is of the “ subrecurva” form and the other 
a smaller and sharply beaked skiff-shaped shell. 
The Blackdown species are :— 
N. impressa, Sy. L. lineata, Sby. 
N. obtusa, Sby. L. angulata, Sby. 
N. antiquata, Sby. 
And for the Grey Chalk :— 
N. pectinata, var. crete, Gardn. N. impressa, Sdy. 
N. obtusa, Sby. | L. lineata, Soy. 
In the Grey Chalk we have apparently Blackdown species, with 
the noteworthy addition of a small form of WV. pectenata. Their 
condition, however, does not permit of the minute comparison neces- 
sary to determine them with the same exactitude as other Cretaceous 
species. The White Chalk has proved hitherto singularly barren of 
Nuculidee, and I have not even met with specimens from the Antrim 
chalk, which is otherwise rich in bivalves and gastropods, so that 
we are wholly without information in the British area as to the 
further development of the genus until the Hocene period. The 
considerable lists of species, however, from the Cretaceous of Lim- 
burg and Aix-la-Chapelle, show that they are by no means absent 
from the newer Cretaceous faunas; and there is no doubt that further 
collecting in the chalk of Ireland and Scotland would enrich our 
fauna with a few additional species. 
All the Gault species have been examined by Dr. Gwyn Jeffreys, 
with the result that he is only able to connect NV. impressa among 
the ‘‘ Ovate” with an existing species, IV. nitida of Sowerby, so 
that the remaining types must be regarded as extinct. He remarks 
