40 MALACOZOA. CEPHALOPODA. FORAMINIFERA. 



GENUS 10. DENTALINA. DENTALINE. 

 Shell subcylindrical, somewhat tapering, more or less 

 arcuate, composed of numerous more or less oblique cells 

 disposed in a single series ; aperture small, submarginal. 



1 . Dentalina linearis. Semistriated Dentaline. 



Shell elongated, subcylindrical, tapering a little toward the 

 lower end, glossy, white, in its lower half marked with distinct 

 longitudinal, somewhat oblique striae and ridges ; of fourteen 

 somewhat oblique, transparent cells, rendered apparent by the 

 opaque white dissepiments more than by the contractions, 

 which are very slight ; the lower end rounded ; the last cell 

 convex, with the aperture very small, circular, with a slightly 

 thickened margin, and placed toward one side. Length two- 

 twelfths of an inch, breadth about an eighth of the length. 



This is evidently Nautilus linearis of Montagu, which how- 

 ever he represents as straight, with the cells transverse, and 

 the mouth produced. 



Found by me among shell sand, from the Bay of Cruden, 

 sent in November, 1842, by Mr. Alexander Murray. 



Nautilus linearis, Mont. Test. Brit. Supplt. 87. PI. 30. f. 9. 

 Orthocera linearis, Flem. Brit. Anim. 236. 



CLASS II. PTEROPODA. 



Body partially covered by the mantle, and frequently 

 furnished with a shell ; head distinct, destitute of arms ; 

 the sides of the neck with membranous appendages for 

 swimming. 



Aporobranchiata, Blainville. Pterdpoda, Cuvier. 

 ILrepov, Wing ; TroSa, feet. 



No species of this class has hitherto occurred to me 

 on our coast. The Pteropoda are of small size, organ- 

 ized for swimming, and for the most part inhabit the 

 tropical seas, although some species occur in vast abun- 

 dance in those of the polar regions. 



