146 GASTEROPODA OF THE INFERIOR OOLITE. 
perfectly reticulate pattern. The longitudinal ornament becomes slightly weaker 
in the body-whorl. The upper row of spirals is rather more nodular and salient 
than the others. Other indications wanting. 
Relations and Distribution—This little shell seems to contain the germ of the 
muricatum-group. It is met with sparingly in the Blue-Wyke Sand-rock, which 
may be regarded as mainly in the opalinus-zone.' It is also quoted from the 
Jurensis-zone by Tate and Blake. 
The Muricatum-Group. 
63. Cerrruium MukIcATUM, Sowerby, 1825 (Dogger variety). Plate VIII, figs. 2 a, 2b. 
1825. Turrireria Muricata, Sowerby. Min. Conch., vol. v, p. 159, pl. 499, 
figs. 1 and 2. 
1829. = _ _- Phillips, Geol. Yorkshire, 1st ed., vol. i, 
: p- 135, pl. iv, fig. 8. 
1844. Curirn IUM GRANULATO-costatuUM, Miinst. (pars). Goldf., Petrefact. Germ., 
vol. iu, p. 82, pl. elxxiii, 
fig. 10. 
1884. — MurtIcaTUM, Sow. WUudleston Geol. Mag., dee. iii, vol. i, p. 51, 
pl. iii, figs. 1 and 2. 
Bibliography, §c.—Speaking in general terms C. muricatum, Sow., represents a 
group rather than a species, nevertheless fig. 2 a is taken from one of Sowerby’s 
types. I have discussed this question at considerable length in the “ Paleontology 
of the Yorkshire Oolites” and will merely repeat my conclusions, viz. that in the 
Yorkshire Dogger there are many varieties of Cerithia, such as those now figured 
and others not figured, which are so plainly connected that they cannot be separated 
specifically. Some of these, especially Sowerby’s type, cannot be separated from 
certain varieties in the Coralline Oolite of Pickering. 
Description—Length 18—25 mm., spiral angle about 18°. Shell elongate, 
strongly turrited ; whorls numerous, very slightly convex and rather constricted 
anteriorly. Width of whorl to height as 5:3°5. Suture distinct ; ornaments con- 
spicuous, consisting of granulated spiral bands usually four and sometimes five in 
number,’ which decussate with more or less numerous longitudinal ribs, which 
latter usually have a slight inclination from left to right, and are sometimes slightly 
arcuate. ‘The nodes or spinous granulations at the points of intersection are 
drawn out spirally, the upper band being somewhat the strongest. The body- 
whorl is short relatively to the spire and similarly ornamented, but the spiral 
‘ Ammonites of the section, Oxynoticeras, are most characteristic of the Blue-Wyke beds. 
The variety “ sea-lineatum” probably belongs to another species. 
