432 PYRAMIDELLID^E. 



factorily determine ; but they give the foot the appearance of 

 being formed of three lobes, an anterior and two suboval 

 lateral ones with rounded termini. This is the great singu- 

 larity, and malacologists would constitute a genus for it, but 

 in all the essential points it is a decided and typical Chem- 

 nitzia. The operculum is fixed on a plain, not extended lobe ; 

 it has the flap-process or apophysis of the tribe, not in the 

 same plane, but inflexed at right angles ; it is cartilaginous 

 and flexible in this species, and the striae of increment range 

 in elliptical curves, as in the typical Chemnitzia pallida. 



The animal is not lively, at least the only one I have ex- 

 amined was not so ; and it is possible more active creatures, 

 which are exceedingly rare, may cause some modification of 

 the points described. It inhabits the littoral zone, and is 

 unrecorded. Axis tV, diameter -^ unciae. 



A second example has shown, that the transverse groove in 

 the foot does not exist, and that in the first specimen it was 

 due to contraction, which when it is completely developed 

 disappears ; nevertheless the structure is peculiar : at rest it is 

 sub-oval, but divided into two portions by an apparent super- 

 ficial line due to colour ; when fully deployed, the anterior one 

 is constricted, slender, attenuated, capable of great extension, 

 slightly auricled and emarginate, subhyaline white ; the poste- 

 rior portion is sub-oval, short, broad, fleshy, of an opake pale 

 drab, divided by a deep medial longitudinal fissure, that seems 

 almost to separate the integuments into two lobes, forming 

 together a rounded termination with a narrow central emar- 

 gination. 



CH. DE cuss AT A, Montagu. 



Odostomia decussata, Brit. Moll. iii. p. 303, pi. 97. f. 6, 7 ; and iv. 

 p. 281. 



Animal inhabiting a pale drab spiral decussated shell of 

 4-5 volutions; it is hyaline white, except the proboscidal 

 muzzle, that passes for the mentum with some malacologists, 

 which is pale pink or red. The mantle is even. The rostrum 

 of this species is less lobed and more truncate than in its con- 

 geners, but it has at times varying phases ; it is small, sub- 



