EAST AMERICAN SCAPHOPOD MOLLUSKS. 97 



KEY TO THE SPECIES OF THE SUBGENUS POLYSCHIDES. 



Apical notches deep. 



Shell fusiform, length 5 to 6 mm tetrodon, page 101. 



Shell not fusiform. 



Length, 7.45 mm tetraschistus, page 97. 



Length, 8 to 11 mm quadridentatus quadridentatus, page 99. 



Shell slightly compressed; length, 5 to 6 mm. .quadridentatus acompsus, page 100. 

 Apical notches less deep; length, 9 to 10 mm carolinensis, page 102. 



CADULUS (POLYSCHIDES) TETRACHISTUS Watson. 



Plate 17, fig. 1. 

 1879. Siphodentalium tetraschistwn Watson, Journ. Linn. Soc. London, vol. 14, 



p. 521. 



1885. Siphodentalium tetraschistum Watson, Challenger Report (Scaphopoda), 



p. 15, pi. 2, fig. 8. a. , AT 



1898. Cadulus (Polyschides) tetraschistus, Pilsbry and Sharp, Tryon s Man. 

 Conch., vol. 17, p. 148, pi. 23, fig. 1. 



The shell is cylindric, rather evenly curved, convex on the dorsal, 

 and concave on the ventral side, tapering from about the middle to 

 the apex, and slightly contracted about the aperture. There is no 

 very decided localized inflation. There is a remote suggestion of 

 evanescent longitudinal sculpture. 



The apex is slit into four pointed lobes by four unequal, irregular, 

 roucrh-edged, gaping clefts, leaving the lobes one dorsal, one ventral, 

 and^two lateral. Two narrow callus-Hke internal bands are present 

 just within the apex. Measurements are: Length, 7.45 mm.; diameter, 

 9 mm.; anterior aperture, 0.75 mm.; spiral aperture, 0.5 mm 



The type now in the British Museum, was taken by the Challenger 

 near the isknd of Fernando Noronha in 25 fathoms. The species is 

 only known to me by original description, and there are no examples 

 in the National Museum collection. 



CADULUS (POLYSCHTOES) QUADRIDENTATUS Dall. 



1881. Siphonodentalium quadridentatum Dall, Bull. Mus. Comp. Zool., vol. 9, 



1885. Cadulus incisus Bush, Trans. Conn. Acad. Arts and Sci., vol. 6, p. 471, 



1889. CaduL quadridentatus Dall, Bull. Mus. Comp. Zool., vol. 18, p. 428, 



1889. CadulJs quadridentatus Dall, Bull. 37, U. S. Nat. Mu^., p. 76 pL 27, fig. 5. 

 1889. Cadulus quadridentatus,ys.r. indsus, Dall, Bull. 37, U. S. Nat. Mus., p. 76, 



1889. Cadulus quadridentatus Dall, Proc. U. S. Nat. Mus., ^l-/^ ? f 5. 

 1892. Cadulus quadridentatus Dall, Trans. Wagner Free Inst. Phila., vol. 3, 



1898. C^' (Polyschides) tetraschistus 5-«^f ^^f f '/^^.^^^^f J""''^'' 

 Tryon's Man. Conch., vol. 17, p. 149, pi. 23, fig. 7; pi. 28, figs. 1-5. 



