18/3.] MR. R. B. WATSON ON MADETRAN MOLLTJSKS. 375 



Mr. Gwyn Jeffreys says of it, " certainly a new species, but closely 

 allied to R. watsoni;" and he adds that it resembles also R. tenera 

 of Philippi. 



I have called it after my friend, that excellent island-naturalist 

 Senhor Joao Maria Moniz. 



Ri&soa watsoni (Schwartz). (Plate XXXV. fig. 11.) 



Shell conic-oblong, thin, transparent, rather brilliant, glossy; 

 whorls rising somewhat in steps. 



Sculpture. Spiral threads on body- whorl 9- 10, prominent, rounded; 

 first generally smaller than others ; the second forms a kind of 

 shoulder, and along with third and fourth is usually somewhat more 

 prominent than the rest ; the last winds close round the pillar. On 

 the fourth whorl there are four of these threads ; on the third and 

 lower part of second whorl three. In second whorl these threads 

 are abruptly cut off, and are replaced in embryonic shell by about 

 eight non-transparent spiral furrows, parted by fretted ridges yAp 

 inch broad. The interstices of the spiral threads are from two to 

 three times the breadth of the threads, the three higher threads 

 being somewhat wider apart than the others. In these interstices 

 the surface is covered with microscopic spiral scratches, which, 

 however, are neither sharp nor deep enough to interfere with the 

 general glossiness of the shell. Very often these interstices are 

 crossed longitudinally at unequal intervals by 20 to 25 faint ribs 

 (sometimes no more than lines), which do not at all show upon the 

 threads, and which die away at the periphery. 



The labial rib is somewhat remote from the lip, is rather broad, 

 and is very little raised. 



Colour generally yellowish white, flecked along the spiral threads 

 and also (near the suture) in the interstices with opaque white 

 and brilliant ruddy brown patches, often passing over from this 

 into uniform dull white or rich brown. The extreme apex never 

 has a blackish tip. 



Spire long, ending in a perfectly hemispherical top, of which 

 the embryonic tip generally forms the very apex. 



Whorls A\, not so much rounded as angulated by a sloping 

 shoulder below the suture, most strongly marked on left side of 

 shell ; of regular increase. 



Suture very strongly marked, but shallow, somewhat oblique. 



Mouth very well rounded, its curve being only a little contracted 

 across the body, very slightly expanded at lower inner corner. 



Lip sharp and thin, scarce marked on outside by the spiral 

 threads. 



Inner lip very sharp, and so far reflected and projecting as it 

 advances downwards as almost wholly to conceal the pillar, leaving 

 a slight umbilical chink behind it. ' It is thinly continued across 

 the body-whorl to meet the upper corner of the outer lip. 



Sh. M. 5. 4. 3 2 1 



L -066 -02/ -028 -017 -01 -007 -004 



B -038 -025 -027 -035 -025 -01 fi "008 



