PUNCTURELLA. 229 



either lanceolate or oval, on the front slope or at the summit of the 

 cone ; inside there is a plate extending forward forming a conduit 

 to the fissure or a " deck " over it. 



The spiral apex is inclined toward the right side, and the fissure 

 is also a trifle to the right of a median line, when visibly excentric. 

 The surface usually shows minute granules under a strong magnifica- 

 tion. 



The tentacles are short and stout ; eyes with or without pigment ; 

 epipodial row of papillae present. In many of the species a male in- 

 tromittent organ is present, behind the right tentacle. The rows 

 of teeth across the radula are oblique, not transverse, the individual 

 teeth being oblique, so that it is bilaterally asymmetrical. 



This is mainly a deep sea group. It diners from Rimula, Emar- 

 ginula, etc. in having a septum or deck inside ; from Glyphis in 

 having no distinct internal callus around the front of the fissure ; 

 from Zeidora in having the fissure closed, not an open anterior slit. 



Puncturella divides into three sections, which, although used in 

 a generic sense by some authors, have only slight systematic value. 



1. Apex persistent; the fissure in front of it. 



a. Fissure at the summit, - - Section Puncturella s. s. 



b. Fissure halfway between summit and front margin, 



Section Cranopsis. 



2. Apex absorbed in the adult by the short oval fissure, 



Section Fissuri septa. 



Section Puncturella s. str. 



Herein are included species having the recurved apex persistent 

 in the adult ; the fissure at or near the summit ; the internal plate 

 with or without side-props. 



P. noachina Linne. PI. 27, figs. 69, 70. 



Shell oval, elevated, about as high as broad ; slopes nearly 

 straight ; the summit in the middle, apex curving downward behind 

 it, showing a minute spiral whorl on the right side. Fissure situa- 

 ted at the summit, narrow. Sculptured with alternately larger and 

 smaller radiating riblets which are slightly irregular but scarcely 

 beaded, and seen under a strong lens to be studded with minute 

 white specks. Color yellowish-white. 



Interior bluish ; septum small, strongly arched, forming a narrow 

 passage to the slit, strengthened by a low buttress on each side. 



