10 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



Tip: Unknown. 



Sculpture: None. 



Apical features: None. 



Size: Small. , ^ 



Special features: Strongly compressed between convex and con- 

 ^ .-, Compressidens, T^Sigeiii. 



cave sides ^ ^ 



Tip: Unknown. 



Size: Medium 



Family SIPHONODENTALIIDAE. 

 This, the second family of the Scaphopoda (see p 87 for the essen- 

 tial features) , contains the three genera, Entalina S^fon.dentca^um, 

 and Caditlus. These may be roughly diagnosed as to shell charac- 

 ters in synoptical form, as follows: 



Form: Greatest diameter at aperture, strongly curved. _ t._,„,,,i 



Apical features: Nuclear apex round in section, becoming hexagonal. 



Sculpture: Very fine longitudinal nblets. ^ ^^_ 



Size: Small 



Form: Greatest diameter at aperture, strongly curved. 

 Apical features: Apex round in section. 



SculDture- None; highly polished surface. 



Size Small - - - Siphonodentaltum, page 88. 



Form: Greatest diameter not at the aperture. 

 Apical features: None. 



Sculpture: None. ^^ 95 



Size: Small 



Genus ENTALINA Monterosato, 1872. 



1872. ^n^aZma Monterosato, Notizia intorno alle Conch. Foss. di Monte Pelle- 

 grino e Ficarazzi, p. 27. 



Tme —E. tetragona Brocchi (Italian fossil). 



Shell Denmnm-\ike in having the greatest diameter at the aper- 

 ture Very strongly curved, small, and sculptured with ong tu- 

 dina fine riblets The apex (except in the nuclear portion) is 

 angular; in the two American species quadrate. The angled apex 

 and sculptural features suggest a true Denmum, but the form o 

 the foot and other anatomical features indicate a position undei 

 the Siphonodentaliidae. 



This genus needs no further subdivision. 



Genus SIPHONODENTALIUM Sars, 1859. 



1859. Siphonodentalium Saks, Forh. Videnskabs-Selskabet, Christiania, p. 52. 



Tyj)e—S. vitreum S&TS {north 'EuTO^e). _ j- . 



Shell strongly arcuate, slightly tapering with maximum diameter 

 at aperture. Circular in section and without sculpture. Apex 

 large and either simple or cut into lobes. 



