154 GASTROPODA. [Aspidobranchia. 



Genus 2. DELPHINOIDEA, Brown, 1827. 



Delphinoidea, Brown, Illustr. Conch. Gr. Brit., 1827, pi. 51. Type : D. ser- 

 pnloides (Montagu). Delphinoidea, Brown : Katherine ,T. Bush, Trans. 

 Connecticut Acad., x, 1897, 100. 



Shell small, white, consisting of a few convex whorls coiled nearly 

 in the same plane, so that the spire is but little raised ; suture deep ; 

 umbilicus rather large, deep, with rounded walls, showing all the 

 whorls, and not denned by a carina ; aperture oblique, nearly circular, 

 slightly angulated above, not modified by the body-whorl ; peritreme 

 simple, thin, entire, but slightly attached ; columellar edge very slightly 

 or not at all flattened. 



Distribution. Similar to that of Cyclostrema. The type is from 

 Devonshire coast, England. 



1. Delphinoidea lissa, Suter, 1908. Plate 34, figs. 1, la. 



Cydostrema lissum, Suter, P. Mai. S., viii, 25, pi. 2, f. 10, 11. 

 Shell minute, discoidal, thin, smooth, umbilicated. Sculpture : 

 To the naked eye the shell appears to be quite smooth, but a powerful 

 lens reveals subequidistant, strongly undulating, radiate threads ; 

 no spiral sculpture is visible. Colour yellowish-white. Spire flat, 

 the nucleus only being slightly raised. Protoconch of 1 smooth whorl, 

 which is convex, and the first half very often slightly elevated. Whorls 



2, the last flatly convex above, periphery and base rounded. Suture 

 impressed. Aperture subcircular, a little angled above. Peristome 

 continuous, sharp. Outer Up advancing, and producing a distinct 

 notch at the suture. Columella arcuate, slightly thickened. Um- 

 bilicus moderate, open. Operculum not seen. 



Diameter, 1 mm. ; height, 0-6 mm. 



Animal unknown. 



Type in my collection. 



Hob. Lyttelton Harbour, on seaweeds, type (H. S.) ; Titahi Bay, 

 Cook Strait (Miss Mestayer). 



Remark. This species is well characterized by its minuteness, 

 the few whorls, and the microscopic radiate sculpture. 



Genus 3. CIRSONELLA, Angas, 1877. 



CirsoneUa. Angas, P.Z.S., 1877, 38. Type : C. austral is, Angas. Cirsonella, 

 Angas, Man. Conch. (1), x, 16, 107. 



Shell minute, globosely turbinate, smooth, narrowly umbilicated ; 

 aperture circular ; peristome continuous, slightly thickened. (Angas.) 

 Distribution. Australasia. 



KEY TO SPECIES. 



A. Shell with microscopic fine spiral lira? ; perforation partly con- 



cealed . . . . . . . . densilirata. 



B. Shell smooth, growth-lines only. 



. Whorls 4 ; aperture subcircular ; perforation open ; heiuht. 



If mm. .. .. granum. 



(id. Whorls 5 ; aperture ovate ; umbilicus partly concealed ; 



height, 2| mm. . . . . . . neozelanica. 



