378 THE LIAS AMMONITES. 



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

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



Locality and Stratiyrapliical Position. — This specimen \yas collected from the INIiddle 

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



Aegoceras striatum, Reinecke. PI. XLII, figs. I — 5. 



Nautilus striatus, Reinec/ce. Naut. et Arg., No. 32, p. 85, pi. viii, figs. 65, 



66, 1818. 

 Ammonites heptangulakis, Founff and Bird. Yorkshire Coast, 2 ed., p. 263, pi. 



xiv, fig. 1, 1828. 



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



fig. 6, 1830. 



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



— striatus. Burner. Nord-deutsch. Oolith-gebirg, p. 199, 1836. 



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



— — Quenstedt. Flozgebirge, Wiirtembergs, p. 177, 1843. 



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



— HENLEYi, d'Orbiyny. Paleoutol. Francaise Terr. Jurass., p. 280, 



pi. Ixxxiii, 1842. 



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



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



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



p. 76, pi. xviii, fig. 1, 1869. 

 Aegoceras striatum, Tate and Blahe. Yorkshire Lias, p. 281, 1876. 



Diagnosis. — Shell inflated, whorls 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 

 imite 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. — I have already pointed out the error palaeontologists have committed 

 in confounding this shell w^ith the true Aeg. Ilenleyi, Sow., although it had long ago 

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



