EAST AMERICAN SCAPHOPOD MOLLUSKS. 87 



Family SIPHONODENTALIIDAE. 



(For diagnosis see p. 10.) 



Genus ENTALINA Monterosato, 1872. 



1872. Entalina Monterosato, Notizie intorno alle Oonchiglie Fossile cli Monte 

 Pellegrino e Ficarazzi, p. 27. 



The shell, as in Dentalium, is largest at the aperture, tapering regu- 

 larly to the apex; it is strongly ribbed with the apex either of angular 

 or of round section. The foot of the animal expands into a disk, 

 with digitate periphery, and has a median process or filament. 



There are but two species of this genus thus far known from the 

 western Atlantic. 



KEY TO THE SPECIES OF THE GENUS ENTALINA. 



Shell four sided quadrata, page 88. 



Shell five sided platamodes, page 87. 



ENTALINA PLATAMODES Watson. 



Plate 15, figs. 1, 4, 5, 7. 



1879. Siphodentaliwn platamodes Watson, Journ. Linn. Soc. London, vol. 14, p. 



519. 

 1885. Siphodentalium plntamodes Watson, Challenger report (Scaphopoda), p. 13, 



pi. 2, fig. 4.. 

 1889. Dentalimn platamodes, Dall, Bull. 37, U. S. Nat. Mus., p. 76. 

 1897. Entalina platamodes, Pilsbry and Sharp, Tryon's Man. Conch., vol. 17, 



p. 133, pi. 23, figs. 3-5. 

 1903. Dentalium platamodes, Dall, Bull. 37, U. S. Nat. Mus., p. 76. 



The shell is small, finely tapered, strongly curved, especially near 

 apex, five sided, but with four more prominent angles, forming roughly 

 a square; the concave side is divided into two spaces by the fifth more 

 obtuse angle. The extreme end of the apex is round, thin but solid. 

 The color of the National Museum specimens is white, translucent, but 

 the surface is not highly polished. A riblet following closely along each 

 of the four prominent angles seemingly doubles these corner angles. 

 A few longitudinal striae appear close to the angles, but none occupy 

 the central portions of the flat spaces between, leaving them per- 

 fectly smooth, save for some microscopic growth lines. The concave 

 space bisected by a primary obtuse angle referred to as less prominent 

 than the other four tends to carry more of the longitudinal striae than 

 do the other interangle spaces. No apical notch is present. Meas- 

 urements are: 



Length, 0.47 inch; diameter, 0.049 inch (type) (11.94 mm. by 1.27 

 mm.). 



Length, 10.5 mm.; diameter, 1.25 mm.; arc, 1.75 (Kebecca 



Shoals). 



