314 Bvlletin Vanderbilt Marine Museum, Vol. VII 



Area avellana, Lamarck, J. B., Anim. sans Vert., 1819, t. VI, p. 

 38. — Lamy, Ed., Journ. Conchyliol., 1904, t. LIT, p. 136, pi. 5, 

 figs. 1, 2. — Prashad, B., Siboga-Expeditie Monogr. Llll-a, 

 Lamellibranchiata exclusive of Pectenidae, pt. II, Pelecypoda, 

 p. 32 (with exhaustive synonymy) . 



it 



Family: ISOGNOMONIIDAE 



Genus: ISOGNOMON Solander 

 Isognomon perna (Linne) 



Plates 123 and 124 



Type : Linne's type is in the Museum Ludovicse. He states : 

 Habitat in Indiis." Lamarck's type of /. sulcatus is in the Paris 

 Museum. Gould's type of /. eremita, taken by the United States 

 Exploring Expedition at Carlshoff Island, Paumotu Archipelago, 

 deposited in the Philadelphia Academy of Natural Sciences, is 

 identical. 



Distribution : This species, first recorded by Lister in 1685, 

 is vi^idely distributed in the Indo-Pacific region. The species pos- 

 sesses a considerable degree of individual variation, which has 

 given rise to a confusion of names, no less than eight being cited 

 by Dr. Prashad, in his excellent synonymy of the species, based 

 upon his study of the fine series of this shell secured by the "Si- 

 boga" in the Dutch East Indies. 



Material examined : One specimen taken on the reef. Falcon 

 Island, Palm Islands, Queensland, October 7, 1931. 



References: Pecten leviter cavus, etc.. Lister, M., Hist. Conch, 

 libri quat., Londini, 1685, pi. 228, fig. 63. 



Ostrea perna, LiNNE, C, von Syst. Nat., ed. XII, 1767, p. 1149. 



Isognomon peiifia, Pelseneer, P., Siboga-Expeditie, Monogr. 

 LIII-A, 1911, Lamellibranchs, (Anatomy), p. 26, pi. 7, figs. 

 3-8. — Prashad, B., Siboga-Expeditie, Monogr. LIII-C, 1932, 

 p. 85. (Excellent synonymy 1685-1932) . 



