Antiplasmodial high-throughput screening of extracts derived from marine invertebrates collected from northern NSW, Australia, resulted in the methanol extract of the bryozoan <i>Orthoscuticella ventricosa</i> being identified as inhibitory toward the 3D7 strain of <i>Plasmodium falciparum</i>. Purification of this extract resulted in two new bis-β-carbolines that possess a cyclobutane moiety, orthoscuticellines A and B (<b>1</b> and <b>2</b>), three new β-carboline alkaloids, orthoscuticellines C-E (<b>3</b>-<b>5</b>), and six known compounds, 1-ethyl-4-methylsulfone-β-carboline (<b>6</b>), 1-ethyl-β-carboline (<b>7</b>), 1-acetyl-β-carboline (<b>8</b>) 1-(1'-hydroxyethyl)-β-carboline (<b>9</b>), 1-methoxycarbonyl-β-carboline (<b>10</b>), and 1-vinyl-β-carboline (<b>11</b>). The structures of all compounds were determined from analysis of MS and 1D and 2D NMR data. The compounds showed modest antiplasmodial activity against <i>P. falciparum</i> in the range of 12-21 μM.