Ventral view of the viscera of Chtenopteryx sicula, showing the absence of a visceral photophore and the presence of the accessory nidamental gland.
<bdi><a href="https://en.wikipedia.org/wiki/en:Adolf_Naef" class="extiw" title="w:en:Adolf Naef"><span title="Swiss scientist (1883–1949)">Adolf Naef</span></a>
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Originally published in: Naef, A. 1921-23a. Cephalopoda. Fauna und Flora des Golfes von Neapel. Monograph, no. 35. English translation: A. Mercado (1972). Israel Program for Scientific Translations Ltd., Jerusalem, Israel. 863pp., IPST Cat. No. 5110/1,2.