THE MOLLUSCA HEDLEY. 



421 



thrown out of symmetry with most Rissoina. 

 Sculpture as usual with the genus, the longi- 

 tudinal sculpture predominates to begin with ; 

 the third, or first sculptured, whorl show- 

 ing a few stout plications. On the following 

 whorl fine spiral threads are visible in the 

 interstices ; on the whorl beneath these are 

 magnified to substantial lyrse ; *nd on the next 

 or penultimate they have doubled in number, 

 and rival the longitudinal in stature, at their 

 intersection beads appear. On the last whorl 

 the longitudinal, as such, have faded away, their 

 influence showing in fine beads perceptible on 

 the sutural and less distinct on a few of the 

 nearer lyrse; the spiral lyrse have now increased Fig. 12. 



to nearly thirty, the anterior smooth, the pos- 

 terior with evanescent beading. These are sharply raised threads, 

 half the width of their interstices, evenly arranged, extending 

 from th? suture to the anterior point of the shell where they are 

 smaller and more crowded. Aperture almost perpendicular, oval, 

 anteriorly with a short perpendicular spout which falls short of 

 the anterior margin ; columella broad, obliquely and sharply 

 truncated. From this truncation a wide and thick callus extends 

 across the body whorl to the posterior angle of the aperture. Here 

 the lip is sharply bent. The outer bevelled lip projects broadly as 

 a heavy varix crossed by fifteen of the spiral lyrse, the central 

 couple of which are smaller and nearer together. Length 4, 

 breadth 2 mm. 



Five specimens in shallow water in the lagoon. 



The extinction of longitudinal and the supremacy of spiral 

 sculpture is unfrequent in the genus. Such species have been 

 separated by Nevill as the Section Morchiella. From all there 

 included the novelty differs by smaller size, more numerous lyrse, 

 and truncated columella. 



RISSOINA PLICATA, Adams. 



(Fig. 13). 



Adams, Proc.Zool. Soc., 1851, p. 264; Mohrenstern, 



Denk. Akad. Wiss., xix., 1860, p. 125, pi. iii., 



fig. 21; Weinkauff, Conch. Cab., i., 22, 1885, 



p. 23, pi. viii., figs. 5, 6. 



Rissoina turricula, Pease, Proc. Zool. Soc., 1860, 



p. 438. 



Two specimens from Funafuti are thus deter- 

 mined. The species appears to vary greatly in size. 

 Whereas the type is described as being 5| mm. 

 long, the Ellice examples are but 2 mm. The 



Fig. 13. 



