PLEUROTOMARIA. 
299 
name of PI. Isevis,^ and that shell, which differs considerably from his former, is 
distinguished from the present species by its more globose shape and narrower 
convex sinus-band, and by having two or three indistinct spiral lines near the 
suture. It is to be noted that when the surface is worn away it is often difficult 
to separate specimens of our shell from Eu. circularis. 
PI. Melnikovi, Tschernyschew, also appears to be an extremely elongated 
variety. Being only figured as a cast, however, it is possible that the ornamenta- 
tion may prove different. 
I am not very certain whether PI. Viennayi, CEhlert, should be regarded as a 
synonym of the shorter variety ; the only distinction seems to be that the sinus- 
band is situated slightly higher on the whorls than usual. 
PI. sublsevis, F. A. Romer, and, as far as can be judged, PL Lydia, Billings, 
seem accurately to agree with some of our varieties. 
Affinities. — In 1817 Sowerby described a shell from the Carboniferous of 
Derbyshire under the name of PI. cirriformis^ but both his figure and description 
are too indistinct to be recognisable. In the ' Geol. Trans.' ^ he doubtfully 
identifies with it a water-worn cast from Plymouth, remarking that the true 
PI. cirriformis is found at Paffrath and is the PI. delphinuloides of foreign authors. 
The Plymouth shell is, I believe, really a specimen of PL seminuda ; while an 
examination of Sowerby's type specimen of the original PI. cirriformis, which is 
now in the British Museum, shows that it is totally distinct from either. The 
shape of its whorls is different ; the sinus-band is elevated, flat, narrow, and 
very coarsely marked with irregular arched strige ; the surface above the sinus- 
band is finely but distinctly cancellated. I do not think that any of the Pleuro- 
tomarise from Devonshire can be referred to Sowerby's species. 
D' Archiac and de Verneuil suggest that PL vittata, Phillips,* should be regarded 
as an intermediate variety, and there is certainly nothing in either Phillips' figure 
or description to differentiate it. His type specimen, however, and other 
specimens in the British Museum show that it is quite distinct. Its shape is much 
more elongate and ovoid, its whorls are more evenly rounded, and its sinus-band 
is flatly convex and bounded by depressed striae. Moreover its growth-lines are 
finer and there is no umbilicus. In general shape it somewhat resembles the 
shell referred by me to Natica meridionalis, Phillips. It is placed by de Koninck 
in his sub-genus Bhineoderma. 
The shell described as PL delphinuloides ? by de Koninck^ (with a long 
1 1850, F. A. Eomer, ' Beitr.,' pt. 1, p. 37, pi. v, fig. 27. 
2 1817, Sowerby, ' Min. Conch.,' vol. ii, p. 160, pi. I7l, fig. 2. 
3 184.0, ibid., ' Geol. Trans.,' aer. 2, vol. v, pt. 3, pi. Ivii, fig. 17. 
* 1836, Phillips, ' Geol. Yorks.,' vol. ii, p. 228, pl. xv, fig. 24. 
5 1842-4. de Koninck, ' Desc. Anim. Foss.,' p. 377, pl. xxxvi, fig. 4. 
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