294 W. H. Sndleston — On the Yorkshire Oolites. 



whorls, but in the apical whorls extend throughout ; they are stout, 

 and occur at intervals about three times their width. A system of 

 fine lamellar lines or striae crosses the shell obliquely from left to 

 right, and is especially conspicuous in the posterior half of the 

 body-whorl. 



Belations and Distribution. — The Yorkshire specimen figured on 

 Plate IX. may perhaps be regarded as a variety rather than an actual 

 representative of the Normandy " Troclms " ornatissimus. Moreover, 

 some of the most distinctive features, such as the pointed ends of 

 the ribs, have been modified by abrasion, whilst the adherence of 

 the matrix prevents a full examination of the basal periphery ; 

 yet I apprehend that this was crenulated, and not plain as in Onustus 

 pyramidatus (lamellosus). Moreover, the greater space between the 

 ribs presents a clear character for separating the two, though I 

 doubt not the existence of intermediate forms. Indeed, the York- 

 shire specimen itself would in some respects serve to illustrate this. 



Though probably the majority of the Dogger specimens quoted as 

 " Troclms " pyramidatus are the representatives of Onustus lamellosus, 

 yet here and there one meets with fragments more resembling this 

 species. " Trochus " ornatissimus is quoted by Lycett from the 

 Inferior Oolite of the Cotteswolds, and the White Oolite (Inferior 

 Oolite) of Ponton in Lincolnshire. 



60. — Onustus pykamidatus, Phillips, 1829. Plate IX. 

 Pigs. 2a, 2&, 3a, 3&. 



1829 and 1835. Trochus pijramidatus, Bean MS. Phillips, G.T. p. 129, pi. xi. 



fig. 22. 

 1852. Trochus lamellosus, D'Orbigny. Terr. Jurass. ii. p. 270, pi. 311, figs. 11-13. 

 1875. Trochus pyramidatus, Phillips, G.Y. 3rd edition, p. 259, pi. xi. fig. 22. 



Bibliography, etc. — Lycett (op. cit. p. 103) considered Phillips's 

 species to be the same as Onustus lamellosus. This is described by 

 D'Orbigny as a large species with a spiral angle ranging from 

 84°-90°, very much wider than high, infimdibuliform, and with 

 a well-marked umbilicus. General structure as in " Trochus " orna- 

 tissimus. He observes that the whorls have no prominence, and that 

 they are ornamented "en travers " by oblique flexuous ribs rather 

 close together, and all crossed by fine oblique striee. 



Description. — Specimen from the Dogger (zone 1), Peak (Blue 

 Wyke). York Museum. Type kefiguked. Figs. 2a, 2b. 



Height 17 millimetres. 



Width 23 „ 



Spiral angle 80°. 



Shell short, trochiform, scarcely umbilicated. The flanks of this 

 specimen have undergone so much polishing that the ornaments are 

 somewhat abraded. Hence the concavity of the upper part of the 

 whorls is less obvious, and the whole outline of the spire more like 

 that of a Trochus. To this circumstance may also be due the ap- 

 parently smaller spiral angle. The costge are separated by a space 

 about twice their width : the anterior portion of the body-whorl is 

 entirely destitute of these axial costae and shows a series of lamellae 

 sloping from left to right. 



