Hlawiceras is an extinct genus from a well known subclass of fossil cephalopods known informally as ammonites that lived during the Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 Period, which lasted from approximately 200 to 145 million years ago.

Hlawiceras belongs to the family Stephanoceratidae

Stephanoceratidae

Sephanoceratidae is a family of planulate and coronate ammonites within the Stephanocerataceae. Shells are evolute so that all whorls are exposed and have strong ribbing that bifurcates, that is splits in two, on the flanks. Many have tubercles at the point of bifurcation...

,true ammonite

Ammonitida

The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....

s, which is contained in the Stephanocerataceae

Stephanocerataceae

Stephanocerataceae is a superfamily of middle Jurassic ammonoid cephalopods within the order Ammonitida containing diverse forms, generally with sharp ribbing and complex suture lines...

. It is probably synonymous with the better known Garantiana

Garantiana

Garantiana is an extinct genus from a well-known class of fossil cephalopods, the ammonites. It lived during the Jurassic Period, which lasted from approximately 200 to 145 million years ago....

Hlawiceras(Garantiana) has an evolute discoidal shell with a subcircular cross section and close spaced transverse ribbing.