EAST AMERICAN SCAPHOPOD MOLLUSKS. 131 



Pilsbry and Sliarj) in their monograph just referred to placed 

 under Gadila many species with shells having less distinct apical 

 characters than the shells of Polys chides, to include which I have 

 proposed the subgenus Platyscliides. 



By removal, then, from this subgenus to Platyscliides of all those 

 species Avith shells having shallow apical notches and lobes, the 

 American rei)resentatives of Gadila are now reduced to a few species 

 of small and even minute shells. These fall within four recognizable 

 groups : 



1. Those having shells of a "bent" or ''canine tooth" appearance 

 owing to a slightly carinated equator and an oblique anterior aperture. 



2. Those with small and even very small shells, having a median 

 equator. 



3. Those of uniform diameter throughout, with orifices of equal 

 diameter. 



4. Those with exceedingly slender, needle-like shells having the 

 equator just back of the anterior aperture. 



The dividing line between Gadila and Platyscliides is often made 

 obscure by the obliteration of apical characters through injury to the 

 thin and fragile rim of the apical orifice. Were these subgenera 

 based, however, upon any very solid foundation of biological charac- 

 ters their importance might demand a greater care in the referring of 

 species to a fixed and exact place under them. 



The species grouped under 1. are Cadulus sauridens, C. rastridens, 

 and C. mayori. 



CADULUS (GADILA) SAURIDENS Watson. 



Plate 19, fig. 11. 



1879. Cadulus sauridens Watson, Journ. Linn. Soc. London, voL 14, p. 525. 

 1885. Cadulus sauridens y^ATSON, Challenger Report {Scaphopoda) p. 19, pi. 3, 



fig. 4. 

 1898. Cadulus (Gadila) sauridens, Pilsbry and Sharp, Tryon's Man. Conch., vol. 

 17, p. 173, pi. 25, fig. 56. 

 The shell is small and narrow, slightly compressed, a little bent, 

 with the equator about median, showing a swelling on the convex 

 side. The convex side describes an even arc. The concave side has 

 its greatest curvature posteriorly; elsewhere it is almost straight 

 with a slight convexity at the equator. The anterior aperture is 

 small, very oblique, and the peristome is thin. There are "very 

 faint microscopical traces of longitudinal texture." The apical 

 features are "chipped." Measurements are: 



Length, 3 mm.; diameter, 0.5 mm.; anterior aperture, 0.25 mm.; 

 a]:>ical aperture, 0.23 mm. (Watson). 



The type is in the British Museum, and was dredged at the Chal- 

 lenger Station 24, ofT Culebra Island, in 390 fathoms, bottom of 

 Pteropod ooze. 



