RISSOA. 



37 



and from typical specimens of the latter in tlie British 

 Museum. It is also the R. subcostulata of v. Mohren- 

 stern. I regard R. similis of Scacchi as a small variety. 



to' 



18. R. stria'ta*, Adams. 



Turho sfriatics, Ad. in Tr. Linn. Soc. iii. p. GG, 1. 13. f. 25, 26. B. striata, 

 F. & H. iii. p. 94, pi. kxviii. f. 8, 9. 



Body white, with a tinge of yellow : pallial filament nearly 

 hyaline, and pendent : snout rather long and narrow : tentacles 

 cylindrical, very finely and closely ciliated : eyes black, almost 

 sessile : foot narrow, truncated in front and slightly auricled, 

 contracted in the middle, and tapering behind to a round point : 

 appendacie short, white, and pointed. 



Shell oblong, inclining to cylindricM, rather solid, nearly 

 opaque, and usually lustreless : sculpture, numerous thread- 

 like spiral striae, of which there are about 20 on the body- whorl ; 

 frequently the upper part of each of the three next whorls 

 (and occasionally also the body-whorl) has a few longitudinal 

 slightly flexuous ribs, that reach only about halfway down 

 and are crossed by the spiral striae ; the two uppermost whorls 

 are quite smooth and glossy : colour white or various shades of 

 yellow, with sometimes two indistinct but broad reddish- 

 brown bands round the middle of the last whorl, which do not 

 extend to the mouth : spire elongated, with a blunt point : 

 it/^or/.s 6, somewhat compressed, gradually enlarging, the last two 

 being nearly equal in breadth, and the largest occupying about 

 three -fifths of the spire : suture very distinct and rather deep : 

 mouth proportionally small, having a somewhat flexuous out- 

 line : outer lip thin, mostly strengthened outside by a thick 

 rib : inner lip reflected, and forming with the other hp a com- 

 plete peristome : operculum transparent, and delicately stri- 

 ated. L. 0-125. B. 0-05. 



Yar. arctica. Without longitudinal ribs or coloured bands. 

 R, arctica, Loven, Ind. MoU. Scand. p. 24. 



Habitat : All our coasts, under stones and at the 



base of seaweeds on the recess of spring tides ; living in 



clusters. It inhabits also the laminarian and coralline 



zones ; and I have dredged it in upwards of 80 fathoms. 



* Striated. 



