Blanfordiceras is a strongly ribbed, evolute ammonite

Ammonite

Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...

 included in the perisphinctacean

Perisphinctaceae

Perisphinctoidea, formerly Perisphinctaceae, is a superfamily of Middle Jurassic to Lower Cretaceous ammonites, commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter....

 family, Neocomitidae that lived during the latest Jurassic.
The shell of Blanfordiceras is discoidal, coiled evolutely with all whorls visible so as to have a broad umbilicus. Exposed whorls are ornamented with strong ribbing that arises from the umbilcus, bifurcating on the outer flanks and extending onto the venter. In general form Blanfordiceras is similar to Berriasella

Berriasella

Berriasella is a discoidal evolute perisphinctacean ammonite, and type genus for the neocomitid subfamily Berriasellinae. Its ribbing is distinct, consisting of both simple and bifurcated ribs that extend from the umbilical seam across the venter; its whorl section generally compressed, the venter...

, although with a more rounded whorl section.