Aspidoceras

Aspidoceras is an extinct ammonoid cephalopod genus that lived during the Late Jurassic. 

Aspidoceras has an evolute shell with quadrate-rounded or depressed whorls that have two rows of tubercles, the outer near the middle of the whorl sides. The outer row soon fades in many species. Some species are also ribbed. The venter, or outer rim, is generally wide and broadly arched.