370 MR. R. B.WATSON ON MADEIRAN MOLLUSKS. [Mar. 18, 



spirally round the base from the junction of the lip and the body- 

 whorl ; below this furrow is a strong spiral ridge, which takes its 

 rise exactly from the upper corner of the mouth ; below this ridge 

 is another furrow, deeper and broader than the previous one. The 

 labial rib is broad and thick, not notched as in R. costata, and is 

 separated from the edge of the mouth by a sharp projecting flange. 



Spiral threads, on last whorl above the basal furrow and ridge 7, 

 on penultimate 5, on preceding whorl 3, on the top whorls none. 

 These threads are clear and transparent, and form knots where they 

 cross the longitudinal ribs ; their interstices are exquisitely crisped 

 (whence the name) with microscopic spiral striolations, faintly 

 crossed by longitudinal sinuous frettings. The 1^ whorl is em- 

 bryonic, cut off by a distinct longitudinal line, and carries five to six 

 minute raised threads, between which in very fresh specimens there 

 is some faint trace of the spiral striolations. 



Colour clear white, as if frosted, with more or less of an orange 

 tinge. Embryonic whorls opaque white, caused by something in the 

 interior of the whorl, not arising from the colour of the shell itself. 



Spire rises in steps, rather short, ending in a small round 

 projecting point, which is not formed by the extreme tip of the 

 embryonic whorl, that tip being a little introverted or immersed. 



Whorls 5 to 6, rounded, the last of rapid increase. The first is 

 often broken ; when present it appears strongly flattened or hollowed, 

 and is thrown up on one side from the immersion of the tip. 



Suture almost effaced by the upward extension of the longitudinal 

 ribs, but between these deep, and behind them slightly channelled. 



Mouth small, rounded oval ; very bluntly pointed above ; ex- 

 panding at the lower inner corner. 



Outer lip very thick, with 12 to 13 sharp knobs on its exterior 

 profile, one of them, the end of the great basal ridge, being often 

 very large. Along its whole sweep it is defined by a concentric 

 ridge on its outer, and by another on its inner edge ; between these 

 ridges is a furrow-like excavation. It is slightly sinuated above. 

 The labial varix is distinctly disjoined from the preceding whorl by 

 the channel of the suture. 



Pillar-lip extremely thick, scored across by four strong twisted 

 ribs ; its inner side is formed by the internal ridge of the outer lip, 

 which is continued all round the mouth. 



Operculum thin, yellow, striated with strongish lines and finer 

 ones intermediate. 



Hab. Gorgulho, shore ; Monte de Piedade (Canical), 25 to 35 

 fathoms ; Ponta de Sao Loureuco, 25 to 45 fathoms ; Santa-Cruz Bay, 

 10 to 15 fathoms; Porto Santo, 50 fathoms; Funchal Bay, 50 

 fathoms ; Teneriffe (M'Andrew's dredgings). 



This species resembles R. zetlandica, but is broader ; the spiral 

 ribs are more numerous, and its apex is more flattened and lop- 



