136 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



The embryonic shell (Fig. B) consists of 2| whorls, and measures 

 alt. 4' 7 mm., breadth 4 mm. It is ovate in form, and very narrowly 

 perforate, the columellar lip being reflected over the perforation, 

 and showing an oblique but almost obsolete fold. The periphery 

 is distinctly angled, and above this angle the shell is furnished with 

 about a dozen very strong and regular spiral striae. These striae are 

 well shown in Preston's photograph of the apex of the shell (Fig. 25J5). 

 Near the aperture the spiral striae are crossed by other less regular 

 striae parallel to the outer lip. 



The parent shell (Fig. A.) agrees closely with Preston's description, 

 only differing from the original specimens of the species in being very 

 slightly more slender. The umbilicus is not quite so narrow as in 

 the embryo, and there is no trace of a columellar fold. The peripheral 

 angle disappears completely during the course of the last whorl. 

 The yellowish periostracum is very faintly marked with numerous 

 spiral lines, but the spiral striae of the protoconch are entirely absent 

 from the post-embryonic whorls, and the oblique riblets which take 

 their place become less pronounced on the lower whorls. Under 

 the microscope exceedingly fine striae can be seen parallel to the 

 lines of growth. 



The foot (Fig. E) is broadly rounded at the hinder end, and has an 

 undivided sole. Deep peripodial grooves cut ofi a broad foot- 

 fringe, crossed by numerous transverse grooves. There is a rather 

 poorly developed caudal mucous gland, opening by a vertical slit. 

 A median longitudinal groove is present on the top of the hinder 

 portion of the foot. 



The mantle-edge (Fig. F) bears well-developed right and left 

 body-lobes, the left being divided into two portions connected by a 

 low ridge. The jaw (Fig. C) is about '2 mm. broad, strongly arched, 

 of moderate thickness, and vertically striated. The radula of the 

 full-grown specimen (Fig. 7) measures about 5 X 2" 2 mm. when 

 flattened out. The central tooth is very narrow, with a single, 

 very small degenerate cusp. The lateral and marginal teeth are 

 bicuspid, having large mesocones and small ectocones, the mesocones 

 of the marginal teeth being particularly long in comparison with the 

 size of the quadrate bases. The mesocones are furnished with lateral 

 flanges, the inner flange being the' broadest, especially on the first 

 lateral tooth, where it overlaps the base of the central. The trans- 

 verse rows of teeth are not quite straight, but trend slightly forwards 

 on each side of the middle line. The radular formula is 

 (30 + 13 + 1 + 13 + 30) X 83. 



The embryonic radula is specially interesting. The specimen 

 examined has fifty-nine rows of teeth, and measures (when flattened 

 out) about 1'4 mm. in length. In breadth it increases from 

 •25 mm. at the front end to "6 mm. at the hinder end. Besides 

 being smaller, the teeth near the hinder end of the radula (Fig. H) 

 differ from those of the adult in beins somewhat broader in 



