34 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Looking over the material of Amphidromus quadrasi Hidalgo 

 before me, and all the printed matter relating to it, I am strongly 

 inclined to believe that a large amount of the material which has 

 found its way into collections consists of shells purchased from 

 natives at Balabac. It is equally probable that these may have come 

 from many of the smaller islands surrounding Balabac Island and 

 that when careful collecting has been done in these places we may 

 find constant races of Amphidromus quadrasi on them just as in the 

 case of CocMostyla ovoidea in other parts of the islands. 



My belief in this is strengthened by the fact that the 86 specimens 

 collected by the Albatross expedition at Caxisigan Island; also the 

 107 from^Bekin, as well as the 41 from Candaraman Island, are of 

 perfectly uniform shape and coloration. This is also true of the 50 

 specimens labeled Southern Palawan without specific locality. 



AMPHIDROMUS QUADRASI QUADRASI Hidalgo. 



Plate 1, fig. 11 ; plate 17, figs. 1-11. 



Amphidromus quadrasi Hidalgo, Journ. de Conch., vol. 35, 1887, p. 36, 



pi. 2, fig. 2. 

 Amphidromus quadrasi Hidalgo, Journ. de Conch., vol. 36, 1888, pp. 33-34. 

 Amphidromus quadrasi Hidalgo, Mem. Real Acad. Sci. Madrid, vol. 14, 



1889, pp. 17-18. 

 Amphidromus quadrasi, var. a.b.d. Smith, Ann Mag. Nat. Hist., ser. 6, vol. 



11, 1893, p. 351, pi. 18, fig. 10. 

 Amphidromus quadrasi Fulton, Ann. Mag. Nat. Hist, ser. 6, vol. 17, 1896, 

 p. 85. 

 Amphidromus quadrasi Eleea, Cat. Sist. Faun. Filip, 1896, p. 618. 

 Amphidromus quadrasi von Mollendorff, Abhand. Naturf. Ges. Gorlitz, 



vol. 22, 1898, p. 149. 

 Amphidromus quadrasi Hidalgo, Mem. Real Acad. Sci. Madrid, 1898, pi. 

 100, figs. 5-6. 



Shell sinistral, regular, elongate-conic. Early whorls white, 

 nuclear whorls two, well rounded, marked with numerous very fine, 

 evenly scattered granules, post-nuclear whorls appressed at the sum- 

 mit, smooth, excepting very fine, decidedly retractive lines of growth 

 and numerous exceedingly fine spiral striations. Sutures only 

 slightly constricted. Periphery of the last whorl angulated in young 

 shells, and very feebly angulated in the adult; base well rounded, 

 marked like the spire. Aperture moderately large, oblique ; outer lip 

 reflected; inner lip moderately reflected. Parietal wall glazed with 

 a thin callus. The coloration of typical quadrasi is as follows: 

 Early whorls white, without dark spot at tip of the nucleus; the rest 

 yellow marked with numerous fine, decidedly retractive green lines 

 which tend to become fused toward the latter part of the shell and 

 give this a green aspect. These green lines do not quite extend to 

 the summit. The summit is marked by a very slender yellowish- 

 white line. This is followed by a moderately broad red band which, 



