112 GASTEROrODA. 



and several oblique ones, at the base of the columella; outer 

 lip thin, slightly inflected. One-third of an inch long. In- 

 habits the sea at Dunbar. 



Genus 11. — AKERA. — Brown. 



Generic Character. — Animal not described. Shell elas- 

 tic, convoluted; apex obtuse, canaliculated, the volutions 

 even with the body ; aperture wide at the base, contracted 

 at top, and extending the whole length of the body; colu- 

 mella visible to the end. 



Akera fiexllis. — The Flexible Akera. Plate XIV. 

 fig. 29. Oval membranaceous, excessively thin and flexible; 

 horn-coloured, with a convolute truncated channelled spire; 

 pillar lip a little thickened and white. Three-fourths of an 

 inch long. Inhabits the British seas. 



Genus 12 DI APH AN A.— i^rozm. 



Generic Character. — Animal unknown. Shell small, 

 spiral, fragile, somewhat orbicular ; aperture encompassing 

 the body, wide ; pillar lip slightly reflected, behind which 

 is a subunibilicus; spire very short, never exceeding two 

 volutions, and hardly rising above the body, which is con- 

 cave at top. 



Diaphana Candida. — The White Diaphana. Plate 

 XIV. fig. 30. Pure white, ventricose ; aperture whole 

 length of the shell, narrowed at top ; spire short ; sub- 

 umbilicated. One-sixth of an inch long. Inhabits the 

 Frith of Forth. 



Genus 13, — ACERA. — Lamarck. 



Generic Character. — Body ovate, convex, transversely 

 divided above into two parts ; the foot with dilatations in 

 the form of fins or wings below; head indistinct; branchiae 

 situated on the back, far behind, and covered by a mantle; 

 no shell. 



