384 PLEUROTOMID^. 



6. P. ne'bula^, Montagu. 



Murex nebula, Mont. Test. Br. (i.) p. 267, t. 15. f. 6. Mangelia nebula, 

 F. & H. iii. p. 476, pi. cxiv. f. 7, and (animal) pi. EE. f. 7. 



Body whitish, minutely speckled with yellow : pallial tube 

 long* and narrow : Jiead small and compressed : tentacles short, 

 diverging, cylindrical from the hase to the eyes, and after- 

 wards becoming less than half the size to the tips : eyes small 

 and black, seated externally on the top of the thickened part 

 of the tentacles, about one-third from their extremities : foot 

 long and broad, truncated or slightly indented in front, with 

 small and obscure angular corners, gradually tapering behind 

 to a blunt point. 



Shell forming an elongated cone having its base or greater 

 diameter just above the periphery, and abruptly attenuated 

 towards the canal ; it is solid, opaque, and of a rather dull and 

 rough aspect : sculpture, strong, broad, rounded, and somewhat 

 prominent longitudinal ribs, from 10 to 12 on the body- whorl, 

 diminishing by degrees upwards ; they are flexuous on the 

 body-whorl, and nearly straight on the upper whorls ; they 

 scarcely extend to the base, and never to the suture, the space 

 below which is spirally sculptured and is margined on the 

 upper whorls by two close-set wavy rows of bead-like striae ; 

 the whole surface (except the apex) is covered Avith very 

 numerous spiral stria), which are crossed by microscopic and 

 oblique longitudinal striro, and reticulated as in the last species ; 

 the spiral striaj are equal in size, and three times as many as 

 in P. hrachy stoma ; the third whorl has three rows of granu- 

 lated striae, the top whorls being smooth and glossy : colour 

 chocolate, with the ribs sometimes of a paler hue : spire some- 

 what turreted, gradually tapering to a rather fine point : whorls 

 10-11, moderately convex, somewhat compressed towards the 

 top of each and sloping downwards ; they are angulated by 

 the ribs ; the last whorl occupies five-elevenths of the shell : 

 suture rather shallow : mouth lozenge-shaped, compressed and 

 acute-angled above, broader in the middle; length four-elevenths 

 of the shell : canal short and wide, turning a little to the left, 

 expanding at the extremity ; basal notch incurved, and con- 

 spicuous outside: outer lip gently curved, slightly bent in- 

 wards ; edge sharp, and closely muricated by the points of the 

 spiral striae : lahial notch rather deep, placed a little below the 



* From its smoky hue. 



