Acera.] GASTROPODA. 537 



long as the shell, narrow above and extending in a deep sinus along 

 the suture, dilated below and very effuse, permitting all the whorls 

 to be seen from the base through the spirally ascending columella ; 

 columella very concave, thin, with narrowly reflexed edge. 



Distribution. Most seas. 



Fossil in the Tertiary. 



The young animals use the parapodial lobes as swimming-organs. 



1. Accra tumida, A. Adams, 1850. Plate 23, fig. 6. 



Bulla (Akem) tumida, A. Ad., Thes. Conch., ii, 573, pi. 125, f. 169. Akera 

 tumida, A. Ad., Conch. Icon., xvi, f. 2 ; C.M.M., 53 ; Crit. List, 38 ; 

 J. de Conch., 1878, 41 ; M.N.Z.M., 122 ; Man. Conch. (1), xv, 379, pi. 42, 

 f. 14. 



Shell horny, fragile, ovately cylindrical, spire rather flattened, 

 semipellucid. tumid in the middle, and rather gibbous near the inner 

 lip, encircled with a faint scarcely conspicuous fuscous band, spirally 

 very finely striated, longitudinally somewhat plicated ; aperture an- 

 teriorly very much dilated. (Ad.) 



Diameter, 10-5 mm. : height, 16 mm. (figure). 



Type in the British Museum (?). 



Hob. New Zealand (Adams). 



The locality requires confirmation. I have not seen this species. 



Subfam. HAMINEIN.E. 



Animal with a quadrate head-disc, bilobed behind ; epipodial lobes 

 large, reflexed over the shell. Principal stomach-plates 3 (Plate 1, 

 fig. 6). 



Shell brittle, with concealed spire ; a posterior sinus, but no sutural 

 slit or anal fascicle ; the interior not wholly visible from base. 



Genus 1. HAMINEA, Gray, 1847. 

 Haminea, Gray, P.Z.S., 1847. Type : Bulla hydatis, L. 



Animal capable of retraction into the shell ; cephalic disc large, 

 truncated in front, strongly bilobed behind, the eyes small. Mantle 

 rudimentary, covered by the shell. Epipodial lobes large, reflexed 

 over and partially covering the shell. Sole long, tapering behind. 

 Gizzard very muscular, armed within with 3 large corneous curved 

 plates, and 3 pairs of small plates. Radula having the formula 

 oo+l + l + l + L-o. Central tooth small, adjacent laterals large, 

 with a long serrate cusp ; uncini many, with long simple cusps. 



Shell thin and rather fragile, unicoloured, corneous, yellowish or 

 greenish, covered with a thin cuticle, globose, ovate, or cylindric- 

 oval, the spire sunken and concealed, vertex concave, imperforate or 

 minutely perforate ; body-whorl large ; aperture as long as the shell, 

 broadly rounded below, narrow above ; columella simply concave, 



