This specimen was collected from the Boone Limestone (Lower Carboniferous) near Hiwasse, Arkansas. It is a species of Syringopora Goldfuss 1826, sometimes known as the organ-pipe coral (but not the real organ pipe coral!).
Syringoporids are tabulate corals, a group that is always colonial. The corallites (tubes that contained the individual polyps) are vertical and were connected by small horizontal tubes, through which they shared common tissue. Some colonies had hundreds of corallites and built mounds up to a meter in diameter. Syringopora is the longest-ranging genus in the family, having started in the Ordovician Period and going extinct in the Permian.
Syringopora was first described by Georg August Goldfuss (1782-1848), a German paleontologist and zoologist. (Goldfuß is the proper spelling, if I can use that fancy Germanic letter.) He earned a PhD from Erlangen in 1804 and later in 1818 assumed a position teaching zoology at the University of Bonn. With Count Georg zu Münster, he wrote Petrefacta Germaniae, an ambitious attempt to catalog all the invertebrate fossils of Germany (but only got through some of the mollusks).
Georg August Goldfuß portrait by von Adolf Hohneck (1812-1879), 1841.
Girty, G.H. 1915. Faunas of the Boone Limestone at St. Joe, Arkansas. U.S. Geological Survey Bulletin 598.
Goldfuß, G.A. 1826-1844. Petrefacta Germaniae. Tam ea, quae in museo universitatis Regia Borussicae Fridericiae Wilhelmiae Rhenanae servantur, quam alia quaecunque in museis Hoeninghusiano Muensteriano aliisque extant, iconibus et descriptionibus illustrata = Abbildungen und Beschreibungen der Petrefacten Deutschlands und der angränzenden Länder, unter Mitwirkung von Georg Graf zu Münster, Düsseldorf.
Nelson, S.J. 1977. Mississippian syringoporid corals, southern Canadian Rocky Mountains. Bulletin of Canadian Petroleum Geology 25: 518-581.