Basinotopus lamarckii (Desmarest, 1822)

Dromilites lamarckii (Desmarest, 1822), Inachus lamarckii Desmarest, 1822 Inachus spec Desmarest, 1822 are all synonyms of Basinotopus lamarckii. 

Basinotopus lamarckii can often be found across many of the London Clay sites, both in Kent and Essex. These sites include Allhalllows, Sheppey, Maylandsea, Aveley Number 2 Pit, Tankerton, Butts Cliff, and Seasalter. It has been recorded at divisions A3, B1, B2, C, D, and E.  

It can be easily identified from its distinctive carapace as seen below. 

Basinotopus lamarckii is now extinct and makes up the Basinotopus genus with Basinotopus tricornis (Collins & Jakobsen, 2003) from Denmark (which is also extinct). It's closest living relatives are from the Superfamily Dromioidea.