MARSHALL ; ADDITIONS TO RRITISH CONCHOLOGY. 207 



fifty per cent, of adult specimens. This excrescence if examined is 

 found to wind itself inwardly round tlie pillar. Sowerby's figure shows 

 an indication of this swelling, though it is usually more prominent. I 

 cannot imagine its utility, nor why it is present in only half the speci- 

 mens. Jeffreys' dimensions are extreme : the usual size is 4jin. by 2in. 

 A dwarf form from the Doggerbank does not exceed 3in. by i-Jin. 



F. turtoni Bean. — Aberdeenshire coast, 70 miles from land, in 

 4of, and from trawlers (Simpson) ! Peterhead, 43f. ('Triton' Expedi- 

 tion) ! East Shetland fishing-banks, from trawlers. This species lives in 

 muddy ground in deep water far from land, rare; more often procured 

 by deep-sea fishermen than by the dredge. The colour is yellowish- 

 white under the epidermis, and occasionally the inside is more or less 

 tinged with purple ; epidermis rather thin, deciduous, ranging from 

 light-brown to olive-green, and frequently stained with ferruginous 

 deposit. Round the periphery the spiral riblets are more prominent 

 and irregular, and these sometimes develop into ridges or carinations 

 (as in F. antiquus var. carinata), thus making the whorls more or less 

 angular at that part. The operculum is large, elongated, and obliquely 

 triangular (but varies greatly in length and width), dark horn-colour, 

 highly glossy, closely wrinkled, with semi-circular striations, and having 

 impressed lines (variable in number) radiating from the nucleus. 



This species is subject to more extreme variation than is generally 

 supposed, and I regard it as by tar the most variable of the genus, 

 while the differences between the male and female forms are more 

 than usually apparent. My smallest adult specimen, from the Shet- 

 lands, is only 3in. by ijin., while the other extreme is represented by 

 examples exceeding 5jin. by 2|in., and there is every intermediate 

 gradation of length and breadth. The whorls also are of every degree 

 of convexity, and the aperture is especially variable according to age, 

 as after it has reached maturity the outer lip is added to and reflected, 

 and the operculum altered to correspond. The shell of the male, 

 correctly figured by Sowerby and Jeffre)s, has a comparatively small 

 body-whorl and an elongated spire, and rarely exceeds 4-Jin. by i-|in. 

 The young of this up to 2in. in length present a very droll appearance, 

 being all spire. An extreme example of this male form from the 

 Shetlands, having the spire abnormally elongated, and now in the 

 collection of Mr. James Simpson, of Aberdeen, has been named var. 

 atteiiuata} The shell of the female, well figured by Forbes and 

 Hanley,- is larger and broader throughout, the spire is not nearly so 

 attenuated, the last whorl is very much larger and swollen, and the 

 shell attains S^in. by 2^in. The young of both forms are easily dis- 



1 Trans. Aberdeen W.M. Nat. Hist. Soc, 1893, p. 83 (with fig.). 



2 Brit. Moll., vol. iii., p. 432; vol. iv., pi. cv., fig. 4; and pi. cvi., fig. 3 (the same shell 

 reversed). 



N 



