1908.1 NATURAL SCIENCES OF PHILADELPHIA. 555 



NOTES ON POLINICES DIDYMA, WITH DESCRIPTION OF A NEW 

 AUSTRALIAN SPECIES. 



BY H. A. PILSBRY AND E. G. VANATTA. 



An Indo-Pacific group of species or forms of the Naticoid genua 

 Polinices is characterized by having a transverse sulcus dividing the 

 convex surface of the dark-brown umbiUcal callous lobe. Numerous 

 supposed species were based on shells of this character, but modern 

 authors have united all under one species, called Natica ampla by 

 Tryon (Manual of Conchology, VIII, 1886) and Natica didynia by 

 Watson and E. A. Smith {Challenger Report, XV, Gastropoda, 1886, 

 p. 450), and by Pritchard and Gatliff {Proc. Roy. Soc. Victoria, XII, 

 1900, p. 191). 



The names which have been apphed to the forms in question follow 

 in chronological order. 



1798. Albula didyma Bolten, Museum Boltenianum, p. 20. Based 



upon Nerita umhilicata livida Chemnitz, Systematisches Conchylien 



Cabinet, V, p. 246, pi. 186, figs. 1856-57 (Tranquebar). 

 1845. Natica papyracea "Busch," PhiUppi, Abbildungen und Be- 



schreibungen neuer oder wenig bekannter Conchylien, Vol. II 



(October), p. 45, pi. 2, fig. 12 (Hab. ?); Conchylien Cabinet, 



p. 87, pi. 13, fig. 4; p. 43, pi. 5, fig. 4. 

 1848. Natica ampla Philippi, Zeitschrift fiir Malakozoologie, p. 156, 



spec. 16 (Hab. ?); Conchylien Cabinet (Natica), p. 41, 



pi. 6, fig. 2. 

 1848. Natica hicolor Philippi, Zeitschrift fiir Malakozoologie, p. 156, 



species 17 (China Sea); Conchyhen Cabinet, p. 43, pi. 6, fig. 4. 

 1848. Natica vesicalis Philippi, Zeitschrift fiir Malakozoologie, p. 159 



(China); Conchyhen Cabinet, p. 40, pi. 6, fig. 1. 

 1846-1858. Natica lamarckii Recluz, in Chenu, Illustrations Conchy- 



liologiques. Vol, III, pi. 2, figs. 1-4. 

 1846-1858. Natica petiveriana Recluz, in Chenu, Illustrations Con- 



chyliologiques. Vol. Ill, pi. 2, figs. 5-9; Reeve, Conchologia 



Iconica, IX, 1855, pi. 5, fig. 17. 

 1846-1858. Natica intermedia Recluz, in Chenu, Illustrations Con- 



chyliologiques. Vol. Ill, pi. 2, fig. 10; pi. 3, figs. 1, 2, 3 (not of 



Philippi, 1836). 



