Mathilda.} GASTROPODA. 273 



corneous, rather solid, multispiral, the external face concave, nucleus 

 central. 



Dr. W. H. Ball classes Mathilda as a synonym of Tuba, Lea, 1833, 

 or at least as a section of it : Trans. Wagner Free Inst., iii, pt. 2, 

 18 ( ,)2, 318. For the present, however, I prefer to consider Mathilda 

 as a distinct genus. 



Distribution. - - Seas of Europe, China, Australasia, Strait of 

 Magellan. There are a number of Tertiary and a few Secondary 

 species. 



Remarks. Dr. P. Fischer writes, '' Mathilda has the shell of 

 Turritella, with the sinistral embryonic whorls of Pyramidella. The 

 exterior form of the animal, the position of the eyes, and the structure 

 of the operculum relate it to the former." 



1. Mathilda neozelanica, Suter, 1908. Plate 15, fig. 12. 

 Mathilda neozelanica, Suter, P. Mai. S., viii, 40, pi. 3, f. 53. 



Shell minute, turriculate, spirally ridged and radially finely striate, 

 imperforate. Sculpture : The first, embryonic, whorl with 4 sharp 

 spirals ; the second with a median spiral and 1 below it ; the third 

 with an additional fine spiral thread upon the shoulder, increasing to 

 2 on the following whorls ; the last whorl with a double keel bounding 

 the base, which is finely spirally striate ; the spiral sculpture reticu- 

 lated by radiate, subequidistant, straight threads, which do not extend 

 upon the base ; interstices microscopically reticulated. Colour white. 

 Spire elevated conic, much higher than the aperture, apex blunt ; 

 outlines straight. Protoconch with the smooth nucleus almost com- 

 pletely immersed in the spire. Whorls 5^, regularly increasing, the 

 upper whorls distinctly shouldered, the last more convex ; base flat. 

 Suture impressed. Aperture rotund, vertical, effuse at the base towards 

 the columella. Outer lip simple, dentate by the sculpture. Columella 

 vertical, slightly arcuate, rounded, very little expanded. Operculinn 

 unknown. 



Diameter. 1-2 mm. ; height, 2-5 mm. 



Animal unknown. 



Type in my collection. 



Hob. Narrow Neck Reef, Hauraki Gulf ; one specimen in sand 

 (H. S.). 



Remark.- The Australian M. decorata, Hedley (Mem. A.M., iv, 

 pt. 6, 352, f. 75 in text), is an allied species, though larger and having 

 a different protoconch. 



Fam. STRUTHIOLARIID^S, Fischer. 



Animal having rather short slender tentacles, with the eyes on 

 short pedicels at their external bases ; foot oval, adapted for swimming ; 

 proboscis long ; siphon scarcely perceptible. Dentition 2+1+1 + 1 + 2, 

 but in some species the marginals increase to 5 ; the central tooth 



