380 MR. R. B. WATSON ON MADEIRAN MOLLTJSKS. [Mar. 18, 



that occupied by the lines. Sometimes these longitudinal lines are 

 interrupted, and a sudden return is made to the spiral-dot arrange- 

 ment ; sometimes, after one, two, or three spiral lines of dots, the 

 longitudinally confluent lines are reverted to. On the base there is 

 much less tendency to this longitudinal confluence of the dots. 

 Round the pillar they are entirely absent ; and this part has always 

 some tendency to be milky white. On the first two whorls these dots 

 are also absent, but two or three series appear on third whorl. In 

 some cases these dots remain projecting when the rest of the surface 

 has weathered off. Besides these crimson dots, and quite independent 

 of them, there appears at the periphery of each whorl a single series 

 of much larger (^^-inch square), opaque (not opalescent nor trans- 

 parent) white spots (whence the name). They are oval or circular, 

 not irregular or indefinite in outline ; ten or twelve go to each whorl. 

 Their lower edge is exactly cut off by the spiral furrow. In the fourth 

 and fifth whorls they lie quite above the suture. They seem much 

 less superficial. than the crimson dots ; but it is they which efface those 

 when they interfere with one another. When the shell is no longer 

 fresh, the crimson of the dots fades to a ruddy brown, and the glassy 

 transparence of the shell becomes troubled ; but some trace of the 

 white spots can generally be discovered to the last. The tip of the 

 shell is opaque white, with no trace of brown stain on embryonic 

 whorl. 



Spire elongated, regularly contracted, ending in a blunt, round, 

 and slightly depressed apex. 



Whorls a\, a little angularly rounded ; the spiral furrow on base 

 produces a very slight carination just below periphery. 



Suture straight, broad, and shallow. 



Mouth small, irregularly quadrangular, caused by the great length 

 and extreme straightness of the pillar, by the angularity of its junc- 

 tion with the body and still more with the outer lip, by the great 

 straightness of the outer lip and its tendency to a slight angulation 

 at its outer and lower corner, and, finally, by the flatness of the basal 

 line. In the young shell these characteristics, though traceable, are 

 not so strongly pronounced as in the old. 



Outer lip sharp, thin, straightish, contracted rather than expanded, 

 at lower corner a little more extended and opener, across base flat- 

 tened and slightly patulous, joining pillar at a distinct angle. 



Inner lip straight, sharp-edged, slightly bevelled back rather than 

 reflected on the long and straight pillar, where it forms a slight and 

 very shallow umbilical chink ; it leaves the pillar a little angularly, 

 and is continued across belly to join outer lip, which it reaches at 

 almost a right angle. 



Hal. Gorgulho, shore; mouth of Ribeiro Secco, Funchal, 10 

 fathoms; Santa Cruz, 10-15 fathoms; Machico, 10-15 fathoms; 

 Piedade (Canical), 15-35 fathoms; Ponta de S. Loureneo, 25-45 



