Peterborough [district, Cambridgeshire], [England] [probably ex.] [Bed 10 (Hudson & Martill, 1994)], Oxford Clay [Formation, Peterborough Member, ("Gryphaea and Reptile Beds")], [*Kosmoceras jason jason* Zone],[Middle Callovian], [Jurassic (Middle)] Previously misidentified as a femur (L). Although formerly only tentatively identified as a ?*Muraenosaurus sp.*, another possibility has arisen: although small, the humerus seems very fully-formed, with flattened articular surfaces for up to 4 epipodials, and thus may possibly be a *Tricleidus sp.* if it is not a *Muraenosaurus sp.*. The distal outline matches specimen V1800 (bar a very slight enlargement on the lateral/radial side), but it is some 25% larger. However, until a more conclusive identification can be obtained, it shall be referred to as *Muraenosaurus sp.*.