84 



32 mètres), Saleyer Anchorage (St. 213), near Lucipara Island (St. 225), Anchorage off Kilsuin, 

 west coast of Kur Island (St. 250) and Tuai Anchorage, Kei Islands (St. 258). 



3. Isognomon isognomum (Linn.) var. norma (Roding). 



1742. Coucha longa bracliiata etc. Gualtieri, Ind. Test., pi. XCVII, figs. A, A, A. 



1770. UEquerre Knorr, Délices des Yeux, IV, p. 19, pi. X, figs. i, 2. 



1784. Species Isognomonis imperfecti anâ Species ciirvali ei gïâôost Isognomonis Chemnitz, Conch.- 



Cab., VII, pp. 253, 256, pi. LIX, figs. 582, 583. 

 1791. Bruguière, Encyclopéd. Méthod., pi. CLXXV, figures 4, 5. 



1798. Isognomon Norma Roding, Mus. Boltenianum, p. 168. 

 18 15. Perna tranquebarensis Leach, Zool. Miscell., II, p. 142, pi. CXIV. 

 1815. Ostrea Isognomum Burrow, Elem. Conch., p. 247, pi. IX, fig. 5. 

 18 19. Perna femoralis Lamarck, Anim. sans Vertèb., VI, p. 140. 

 1825. Perna femoralis Blainville, Man. Malacol., p. 528, pi. LXIII, fig. i. 



1840. Perna femoralis Pfeifîfer, Krit. Reg., p. 71. 



1841. Perna femoralis Sganzin, Cat. Coq. Ile France, p. 10. 



1845. Perna tranquebarensis Chenu, Leach Miscell. Zool., p. 17, pi. VIII, fig. i. 

 1858. Perna isognomum Reeve, Conch. Icon., XI, Perna, pi. V, fig. 24. 

 1862. Perna femoralis Chenu, Man. Conchyliol., II, p. 161, fig. 802. 



1879. Perna isognomon var. femoralis von Martens, Monatsber. K. Akad. Wiss. Berlin, p. 740. 



1880. Perna isognomon var. femoralis von Martens, Mobius Beitràg. Meeresf. Mauritius, Seychell., 



P- Z^l- 



1890. Perna isognomum var. femoralis Paetel, Cat. Conch. Samm., III, p. 206. 



1890 — 91. Perna isogonum and P. obliqua Clessin in Martini-Chemn. Conch.-Cab. (N. F.), VIII (i), 

 Malleacea, pp. 27, 41, 44, pi. VIII, fig. i, pi. XV«, fig. 2, pi. XV^, fig. i, pi. XV(^, fig. 2. 



1891. Perna femoralis Smith, Proc. Zool. Soc. London, p. 435. 



1898. Perna femoralis Melvill & Standen, Journ. Conch., IX, p. 81. 



1929. Isognomon isognomum var. femoralis, Dautzenberg, Faun. Colon. Français., III, p. 566. 



This variety has a more elongate, straight or somewhat arched and even tvv^isted, and 

 a comparatively narrow shell \ the auricles are very small and poorly developed ; the hinge area 

 is also comparatively narrower than in the typical form. 



Distribution : — /. isognomum var, norma appears to be mainly restricted to the Indian 

 Océan, but the "Siboga" Expédition collected a typical shell of this variety at Saleyer 

 Anchorage (St. 2 i 3). 



4. Isognomon atte^iuata (Reeve). 



1788. Ostrea perna Barbut (nec Linn.), Gen. Verm., p. 56, pi. IX, fig. 3. 

 1858. Perna attenuata Reeve, Conch. Icôn., XI, Peryia, pi. VI, fig. 25. 

 1860. Perna attenuata Reeve, Elem. Conch., II, p. 66. 

 1869. Perna attenuata Issel, Malacol. Mar. Rosso, p. 96. 



1890. Pertia attenuata Paetel, Cat. Conch. Samm., III, p. 206. 



1891. Pertia attenuata Clessin in Martini-Chemn. Conch.-Cab. (N. F.), VIII (i), Malleacea, p. 33, 



pi. XI, fig. I. 



1899. Perna attenuata Melvill & Standen, Journ. Linn. Soc. London (Zool.), XXVII, p. 184. 

 19 10. Perna attenuata Hedley, Austral. Ass. Adv. Sci., XII, p. 344. 



Isognomon attenuata appears to be a highly variable species. The shells are usually 

 oblique and rather narrow, but others are broader and somewhat curved about the middle. The 

 hinge-line is short and narrow. It is probably only a form of /. isognomum. 



