122 



CRUSTACEA. 



{Anomura.) 



Basinotopus (M^Coy), n. g.* 



I propose this genus for the reception of a very common cnis- 

 tacean of the London clay at Sheppey, originally figured and 



Diagram of the genus Basinotopus (nat. size). 



a, Male sperimen 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 Crustaces 

 Fossiles ' under the name of Inachus Lamar ckii, but which I have 

 ascertained_, from the examination of numerous finely preserved 

 specimens, not to belong to the genus Inachus, 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- 

 dicating 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 NotopuSy. &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 Anonuuous nature of this fossil, I thought it 

 might be the generic type named DromilUes by Dr. Milne-Edwards in the 

 number of * I'lnstitut ' 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. 



