ENTALINA. 131 



There has been no monograph of Siphonodentaliidce published, or, 

 at least, none of any value ; but a very large amount of information 

 is contained in the works of M. and G. O. Sars, Jeffreys, Watson, 

 Dall and Verrill. Dr. Simroth gives a very valuable general account 

 of the group in the new edition of Bronn's Klassen und Ordnungen 

 des Thier-Reichs, iii, 1895. 



Key to genera of Siphonodentaliidce. 



I. Shell largest at aperture, thence tapering to apex. 



a. Longitudinally ribbed, angular in section at least near the 

 apex, ENTALINA, p. 131. 



a'. Smooth ; circular or subcircular in section throughout, 



SIPHONODENTALIUM, p. 135. 



b. Apex cut into lobes or teeth, Section Siphonodentalium. 

 b'. Apex simple, unslit, Section Pulsellum. 



II. Shell more or less swollen near the middle or anteriorly, con- 

 tracting toward the aperture as well as tapering posteriorly, 



CADULUS,p. 142. 

 a. Apex with slits or notches. 



6. Apex with two lateral slits, Section Dischides. 

 b'. Apex with four or more slits, Section Polyschides. 

 a'. Apex entire, unslit. 



b. Obese ; both ventral and dorsal outlines convex and 

 projecting beyond a chord connecting the adjacent 

 lip edges, Section Cadulus s. s. 



b f . More slender or attenuated ; ventral outline convex; 

 dorsal outline as a whole concave, not projecting 

 beyond a chord connecting the ends of shell. 



Section Gadila. 



Genus ENTALINA Monterosato, 1872. 



Entnlina MONTS., Notizieintorno alle Conchiglie Fossile di Monte 

 Pellegrino e Ficarazzi, p. 27, for D. quinquangulare Forbes. Pul- 

 sellum STOLICZKA and Siphonentalis G. O. SARS, in part. Dentalium 

 sp. of some authors. 



Shell Dentalium-like, largest at the aperture, thence tapering to 

 the apex ; strongly ribbed, and angular in section near the apex. 

 Foot expanding distally into a disk with digitate periphery, and 

 having a median process or filament. Type E. quinquangularis 

 (Forbes). 



