some British Fossil Crustacea. 167 
(Anomura.) 
Basinotopus (M‘Coy), n. g.* 
I propose this genus for the reception of a very common crus- 
tacean of the London clay at Sheppey, originally figured and 
Diagram of the genus Basinotopus (nat. size). 
a. Male specimen seen from above; 6, profile of female specimen showing 
the tumid pterygostomian region and the elevation of the two hinder 
pair of legs over the third pair; c, abdomen of female, showing the tri- 
angular intercalated pieces between the fifth and sixth joints. 
described by Desmarest in his ‘ Histoire naturelle des Crustacés 
Fossiles’ under the name of Inachus Lamarckit, but which I have 
ascertained, from the examination of numerous finely preserved 
specimens, not to belong to the genus Jnachus, nor even to the 
Brachyurous division, but is truly Anomurous, retaining the little 
triangular plate between the fifth and sixth joints of the tail, in- 
dicatng the presence of a caudal fin in the young, and also 
having the two hind pair of feet disproportionally small and ele- 
vated as in Homola, Dorippe and Notopus, &c., from all of which 
it differs in the large peculiar posterior or basal space behind all 
the other regions on the carapace (from which the genus derives 
its name), besides other less striking characters. As there is but 
one species known, which never has been very fully described, I 
subjoin a description comprising the generic and specific charac- 
ters for the present. 
* On recognizing at first the Anomurous nature of this fossil, I thought it 
might be the generic type named Dromilites by Dr. Milne-Edwards in the 
number of ‘1’Institut’ for August 1837 from Sheppey, but having lately had 
the pleasure of showing him the specimens, I find that though closely allied 
they are yet distinct. 
