Leptictis haydeni Leidy, 1868, from the early Oligocene of South Dakota is the type species of the genus and is known only from the well-preserved holotype cranium. The anatomy of its basicranium is described and illustrated based on CT scan data and the primary neurovascular structures are reconstructed. Comparisons are made with a cranium of Leptictis dakotensis (Leidy, 1868) also based on CT scan data. Numerous differences between the two are identified, including the shape of the hypophyseal fossa, the size and orientation of the posterior clinoid process, the depth of the sulcus for the capsuloparietal emissary vein, the size of the petrosal contribution to the middle cranial fossa and to the epitympanic recess, the position of the exit of the auditory tube from the middle ear, the size of the entotympanic, the presence of a styliform process on the entotympanic, and the shape of the ectopterygoid process of the alisphenoid, which added to the few prior reported dental differences justify retaining separate species. The ramus inferior of the stapedial artery, identified by prior authors as present in L. dakotensis, is shown to be absent in both species. Additional comparisons are made with the early Eocene palaeoryctid Eoryctes melanus Thewissen and Gingerich, 1989, also based on CT scans. These three taxa share details of the tympanic processes and epitympanic wings of the bones of the middle ear, the pattern of the dural sinuses and the large size of the sigmoid sinus, the well-developed exposure of the parietal on the occiput, and the unusual course of the nerve of the pterygoid canal, suggestive of a possible close phylogenetic relationship.

One hundred twenty years ago, Carnegie Museum of Pittsburgh, Pennsylvania outbid major institutions in Europe and the United States to purchase the premier private fossil collection of Ernest Bayet of Brussels, Belgium. William J. Holland, Director of the Carnegie Museum persuaded Andrew Carnegie, the museum's founder, to furnish $25,000, a sum totaling over $785,000 today for a collection purchased sight unseen to boost research and exhibition at Carnegie Museum's newly formed Department of Paleontology. Additionally, Holland also sought world class specimens for the planned 1907 museum expansion. Bayet had assembled the bulk of his collection, consisting mostly of European and North American fossils, through purchases and trades with over fifty late 19^th century fossil collectors and dealers. While most of his collection came from purchases, Bayet also embarked on at least one field expedition. In June 1903, Bayet accepted Holland's offer to purchase his collection. In July, Holland travelled to Brussels to organize, pack, and arrange transportation of over thirty tons of fossils, destined for Pittsburgh. Prior to Holland's arrival in Brussels, negotiations proceeded through over fifty letters and at least eight telegrams. In 1903, transatlantic letters could take a week or more to arrive. Telegrams, while more rapid, were limited by expense to short bursts of information. These communication restrictions are one explanation for how misunderstandings about Bayet and his fossil collection took hold. Today, document digitization and online record access provide ways to advance our understanding of the past.

This contribution documents archival sources such as the Holland Archive at Carnegie Museum, the Royal Malacological Society of Belgium, and other European and North American sources. The biographical study of Bayet is the first dedicated to his life and motivations for collecting fossils. It provides details about the roller coaster purchase negotiations, the difficulties of packing and shipping of over two hundred fossil crates, the scientific tensions surrounding research, and a near disastrous storage decision. It also addresses 120 years of misconceptions about Bayet and his collection. Finally, this publication begins the process of recognizing hundreds of Bayet specimens recovered from classic type geologic and stratigraphic locations in Europe and North America.