Natural History - Malachite Slice Group [3]

Phacops speculator specimen on a matrix, clearly showing the external structures. 160 grams, 79 mm



From the Hamar Laghdad Formation, Atlas Mountains, Pragian, (Alnif), Morocco, North Africa. From an old Oxfordshire fossil and mineral collection.

Two Green River fish specimens Diplomystus sp. in a matrix. 243 grams, 15.8 cm



From Wyoming (Green River Formation), USA. From a Lincolnshire, UK, collection.

In southwest Wyoming (and parts of Colorado and Utah) in the Green River Formation are found some of the world's most outstanding specimens of fossil fish. The Green River system was composed of three lakes: Lake Ulinta, Lake Gosiute and Fossil Lake. These Eocene lakes lay in a series of intermountain basins formed by geological events that uplifted the Rocky Mountains during the early Tertiary time. The climate was much different from the desert-like climate of this area today. Both the fauna (crocodiles, alligators, boa constrictors and some subtropical fish families) and the flora (such as large palm trees) indicate a climate much like that found along the Gulf Coast today. Large amounts of ash found in the sediments indicate that volcanoes were particularly active at this time.

Cleoniceras sp. displaying the distinctive pattern of the cross-section chambers. 360 grams total, 11.3-11.5 cm



From Madagascar. Collected between 1930 and 1960. From the collection of the palaeontologist R Gledhill.