Histological sections through Monodelphis at day 10 (A, B) and day 36 (C, D) showing development of respiratory and olfactory turbinals. Sections A and C are anterior to the orbit, through the nasal capsule. Sections B and D are through the orbit, and show the transverse lamina separating the blind sphenethmoid recess from the nasopharyngeal passage just anterior to the choana. Abbreviations: EtT, ethmoid turbinal, Me, mesethmoid; NPP, nasopharyngeal passageway; OB, olfactory bulb; OE, olfactory epithelum; SeR, sphenethmoid recess; SP, secondary palate; TvsL, transverse lamina; VNO, vomeronasal organ; Vo, vomer. Image brightness and background uniformity were adjusted in Adobe Photoshop.