168 



This species is very like the European P. albus, but not spirally 

 striated. 



The most interesting of these shells is a new genus, which appears 

 to belong to the family Lymneadce, and allied to the genus Ancylus, 

 but to be immediately distinguished from it by the shell possessing a 

 thin lamina on the hinder edge of the cavity, most probably extended 

 between the upper part of the body and the upper edge of the foot, 

 as is the case in Crepidula. It is easily to be distinguished from the 

 latter genus by the posterior plate having its edge bent suddenly down 

 towards the base of the aperture and enlarged at the front part of the 

 right side, and produced into a lobe having a groove between it and 

 the inner surface of the right side of the shell. This character also 

 separates it from Navicella. 



The genus may be thus characterized : — 



Latia. 



Shell half ovate, spiral, of one or two very rapidly enlarging whorls ; 

 spire very short, placed nearly in the centre rather on the left of the 

 hinder edge ; aperture very large, nearly occupying the whole of the 

 shell, oblong, rather oblique ; cavity simple, hinder edge with a thin, 

 narrow, flat, horizontal lamina occupying the hinder and nearly half 

 the length of the left side of the cavity ; the left and hinder edge 

 suddenly bent down towards the base of the shell, and produced into 

 a rather broad expansion at the right side, leaving a rather broad 

 space between it and the inner part of the right side of the aperture ; 

 periostraca thin, pale brown, spirally striated. 



Animal. — Head with a short broad snout, rounded in front ; ten- 

 tacula two, short, triangular, the eyes on the outer side of their base ; 

 body subspiral ; mantle submargmal, continued all round ; edge simple ; 

 aperture of the respiratory cavity on the hinder part of the right side, 

 protected on the inner side by the process of the lamina ; upper part 

 of the body subspiral, separate from the back of the foot and fitting 

 into the upper cavity of the shell above the posterior plate ; abductor 

 muscle submarginal, horse-shoe-shaped ? ; foot oblong, rounded at 

 each end. 



The description of the animal is imperfect, being taken from a dried 

 specimen softened by being soaked in a weak solution of caustic pot- 

 ash, and then placed in weak spirits. 



This genus is evidently allied to Ancylus, but differs in the shell 

 being more Nerite-like, and in the aperture of respiration being placed 

 on the right side. 



Latia neritoides. 



Pale brown, spirally striated, internal lamina white, transparent. 



Hub. Auckland, New Zealand. 



Dr. Sinclair sent some specimens of this shell to the British Mu- 

 seum, with animals dried in them, in 1847, and Major Greenwood 

 has kindly sent two additional specimens. 



