338 THE LIAS AMMONITES. 



verse lines of sculpture. In fig. 2 is represented a portion of the outer lamina of the shell 

 showing lines and perforations highly magnified ; in fig. 3 parallel lines formed by a 

 finely-punctated surface are shown. 



The siphonal area is large, convex, and wrinkled transversely in the adult ; the spire 

 is composed of whorls, which are about as wide as they are high, slightly flattened on the 

 sides and only slightly involute. The aperture is nearly quadrate, mucronated on each 

 side at the siphonal area, and gently grooved by the return of the spire. The septa, 

 according to d'Orbigny — I have not seen the lobe-line — are divided into three lobes, of 

 which the two external are formed of pairs of parts. The siphonal lobe is as long and 

 wide as the principal lateral, and ornamented laterally with three branches, of which the 

 inferior is bifurcated. The siphonal saddle, as large as the principal lateral lobe, is divided 

 into three folioles of which the median has three festoons. The principal lateral lobe 

 is divided into two large, nearly equal terminal branches, and four lateral digitations. 

 The lateral saddle is formed of two parts almost equally bi-lobed ; the inferior lateral lobe 

 is oblique, and terminates in two unequal branches, of which the internal is the largest. 

 The accessory lobe is provided with two small unequal points, a radial central line in 

 parting from the extremity of the siphonal lobe touches the points of the principal lateral 

 and passes well above the others. 



Affinities and Differences. — In early age this species resembles Ae^. cajjricornus, whilst 

 in its middle-age and adult conditions it is entirely different; this fact will be demonstrated 

 when the shell-structure and morphology of that species is under discussion. 



Locality and Stratiyraphical Position. — This species is found in the Arietites 

 ohtusus-zone at Lyme Regis, in the same horizon near Yeovil, at Marston Magna near 

 Ilchester, in Robin Hood's Bay, Yorkshire, and the Midland Railway cutting, at Breden, 

 and in other exposures of the same zone in other parts of the Vale of Glo'ster. 



Aegoceras submuticum, Oppel. PI. XXVII, figs. 1 and 2. 



Ammonites matrix oblongds, Quenstedt. Cephalopoden, p. 85, pi. 4, figs. 16 a — d, 



1849. 



— — Oppel. Mittlere Lias Schwabens, Jabreshefte Wiirttem- 



berg, p. 73, pi. 1, fig. 5, 1853. 



— sxJBMUTicus, Oppel. Die Juraformation, p. 158, 1856. 



— Dumortier. Dep6ts Jurassiques du Bassin du Rh6ne, 



torn, iii, p. 63, pi. xii, figs. 1, 2 ; 

 pi. xliv, figs. 2—4, 1869. 



— SUBMUTICUM, Neumayr. Systematik der Ammonitiden. Zeitscbrift 



der Deutsch. geol. Gesellscbaft, p. 906, 

 1875. 



