378 . THE LIAS AMMONITES. 



Affinities and Differences. — This fossil closely resembles some forms of Aeff. capricornus 

 or maculatum, and may be only a variety with more pronounced characters of that species. 



Localiiy and Stratic/rapliical Position. — This specimen was collected from the Middle- 

 Lias Limestone at Charmouth, where it appears to be rare. 



Aegoceras striatum, Eeinecke. PI. XLII, figs. 1 — 5. 



Natjtilds steiatos, Reinecke. Naut. et Arg., No. 32, p. 85, pi. viii, figs. 65,. 



66, 1818. 

 Ammonites heptangulaeis, Youvg and Bird. Yorkshire Coast, 2 ed., p. 263, pi. 



xiv, fig, 1, 1828. 



— STKIATUS, Zieten. Versteinerung. "Wiirttemburgs, p. 7, tab. v, 



fig. 6, 1830. 



— CHELTiENSis, MurcMson. Geol. of Cheltenham, 1st Edit., p. 19, 1834. 



— STKIATUS, limner. Nord-deutsch. Oolith-gebirg, p. 199, 1836. 



— — Bronn. Leth. geog., p. 449, tab, xxiii, fig. 7, 1837. 



— — Quenstedt. Plozgebirge, Wiirtembergs, p. 1/7, 1843. 



— — — Cephalopoden, p. 135, tab. ix, fig. 24, 1849. 



— HENLEYi, d'Orbiffny. Paleontol. Franfaise Terr. Jurass., p. 280, 



pi. Ixxxiii, 1842. 



— — Simpson. Fossils of the Yorkshire Lias, p. 70, 1855. 



— STEIATUS, Quenstedt. Der Jura, p. 134, tab. xvi, figs. 9, 10, 1858. 



— — Dumortier. Depots Jurass. du Bassin du Rhone, III,. 



p. "/&, pi. xviii, fig. 1, 1869. 

 Aegocekas steiatum, Tate and Blake. Yorkshire Lias, p. 281, 1876. 



Diagnosis. — Shell inflated, M'hoiis depressed, one half involute, sculptured with 

 numerous delicate, longitudinal striations ; outer whorl very thick ; sides flattened 

 and provided with two rows of tubercles ; ribs arise near the siphonal suture, and 

 unite in the inner row of tubercles ; from thence sometimes one, sometimes two, short,^ 

 straight, slender ribs proceed and unite in the second series of tubercles which bound the 

 margin of the siphonal area'; from each marginal tubercle nearly always two strong ribs 

 proceed, which pass transversely across the area ; umbilicus small, deep, and narrow ;. 

 inner row of tubercles alone visible in the spiral volutions ; aperture roundish or of a 

 heptangular form. 



Dimensions. — Transverse diameter 130 millimetres; width of the umbilicus 34 milli- 

 metres; height of the aperture 65 millimetres ; transverse diameter 75 millimetres. The 

 smaller specimen has the same relative proportions and dimensions. 



Description.—! have already pointed out the error palaeontologists have committed 

 in confounding this shell with the true Aeg. Henleyi, Sow,, although it had long ago 

 been accurately described by the Rev. George Young in his ' Yorkshire Coast,' who says : 



