PLEUROTOMARIA. 429 
accept this view, and I am inclined to agree with him. Certainly one could fill a 
plate with forms of the Ornate which might possibly be regarded as intermediate 
between Pl. tuberculosa, Defrance, and Pl. ornata, Sow. But under any 
circumstances the fossils we are now considering differ so widely from the average 
form of Sowerby’s species as to merit distinction. Since a name is required, that 
of “ tuberculosa” is certainly appropriate. The type was obtained from “ near 
Caen in the Oolite bed.” 
Description : 
Height : : : : . 25 mm. 
Basal diameter : : : . 55 mm. 
Spiral angle : ; » 1282. 
Shell turbinate, much depressed, widely umbilicate. The spire, though low, is 
regular. Whorls (six) angular, and increasing by wide steps »with a canaliculate 
suture. ‘he angle of each whorl is ornamented with very thick tubercles, and the 
entire shell is pervaded by fine spiral lines, radially decussated in the earlier 
whorls, and undulating towards the anterior margin of the later ones. 
The sinus-band is rather wide, flat and submedian ; its ornaments vary with 
the ornaments of the whorls, but anteriorly have a tendency to disappear, showing 
only sinuous growth-lines. The body-whorl is relatively very large, euomphaloid, 
and bicarinate; the upper keel is grossly nodular ; in the lower keel the nodules 
are drawn out spirally, exhibiting a dentate periphery. Base round, with a large 
infundibuliform umbilicus. Aperture oval, depressed. 
Relations and Distribution.—This is pretty near to Pl. ornata, var. suleifera, 
Deslongch. ‘The form is rare in England. The best specimens come from Louse 
Hill (Humphriesianus-zone). The fossil quoted by Morris as from the “TI. O. 
Bridport ’’ came most probably from Burton Bradstock, whence also I have seen 
specimens of Pl. tuberculosa. 
371. PLEvROTOMARIA oRNATA, Sowerby, 1818. Plate XXXVII, figs. 3 a, 3b, 3c. 
1818. TrocHus ornatus, Sowerby. Min. Conch., pl. cexxi, fig. 1. 
Syn. 1823. — Pattium, Farey. Sowerby, Min. Conch., vol. iv, Index (Corri- 
genda). 
1843. Prevroromarta Patiium, Sowerby. Morris, Cat., p. 158 (edition of 1854, 
p- 271). 
1873. — — Morris. Tawney, Dundry Gasteropoda, p. 49 
(41). 
Bibliography, §e.—So long as this species was referred to the genus T’rochus, 
the name selected by Sowerby was open to Farey’s correction. Subsequently 
