618 GASTROPODA. [Pulmonata. 



elongated oval, slightly broadened anteriorly. Specimens have been 

 found with the septum partly formed, but not adult. 



Length, 3 mm. ; breadth, 2 mm. ; height, mm. 



Jaw very minute, filiform, consisting of a single row of small 

 separate imbricating plates, oblong in shape and serrate at one end. 



Radula having the formula 9 + 5 + 1 + 5 + 9. Central tooth 

 small, with the posterior end of the base broadened, with 2 minute 

 cusps. Laterals bicuspidate ; marginals with 4 cutting-points. 



Type in my collection. 



Hob. River Avon, near Christchurch, mostly on Elodea cana- 

 ili'tisis, below the outflow of Horseshoe Lake. 



SUBORDER 2. STYLOMMATOPHORA. 



Pulmonata with 2 pairs of tentacles (except the AthoracophoridcB 

 and Vertigo, which have only a single pair) ; these tentacles are in- 

 vaginable. and the eyes are borne on the summits of the posterior 

 pair. The male and female genital orifices open into a common ves- 

 tibule, except in the Digonopora (Vaginulidce and Onchididce). A 

 suprapedal gland is. present in nearly all the groups. With the ex- 

 ception of Onchidium. there is no longer a veliger stage in the de- 

 velopment ; the embryo is often furnished with a contractile pedal 

 vesicle. 



The Stylommatophora may be divided into four tribes the Holo- 

 i/itfiitia. A'/ttntha, Elasmognatha, and Digonopora. 



Tribe 1. HOLOC4NATHA. 



Jaw simple, without a superior appendage. 



Fain. ZONITID.E, Pilsbry. 



Animal having the foot-margin defined by a pedal groove ; tail- 

 gland often present, and sole frequently tripartite. Radula with the 

 marginal teeth narrow, the basal plates elongated, and either uni- 

 cuspid and thorn-shaped by suppression of side cusps, or bicuspid 

 by elevation of outer on middle cusp. 



Shell generally heliciform, sharp-lipped. 



The Zonitidce are widely distributed, and appear first in the Car- 

 boniferous. 



Genus 1. FRETUM, Sykes, 1900. 



Fretum, Sykes, P. Mai. S., iv, 1900, 140. Type : Nanina casca, Gould. 

 Eurypus, Semper, Philipp. Landmoll., iii, pt. i, 1870, 36 ; not of Kirby. 

 Aiihicopiis, Pfeffer ; not of Serville (Coleoptera). 



Animal with the shell on the broad back of the foot, which bears 

 on each side a. narrow border with several small lappets. The shell- 

 lobes are variable in size, the left divided into 2 small lobes. Concre- 



