AEGOCERAS MAUGENESTI. 359 



the involution of this species accounts for the fragmentary condition in which it is found, 

 seeing that the volutions have a very feeble support from the turns of the spine. 



Affinities and Differences. — This species very much resembles Aeg. Mau(jenesti, found 

 with it in the same bed. It is distinguished from that species by its more compressed 

 shell and its carina, by its ribs limited to the middle of the whorl, and by the two tubercles 

 between which the ribs are limited. These two Ammonites are certainly very nearly 

 allied, although they are distinct. 



Locality and StratigrapJacal Position. — I have collected this species from the Middle 

 Lias of Leckhampton, near Cheltenham, associated with Aeg. Maugenesti, Aet/. Ibex, 

 and Aeg. Loscombi ; and it is found in the same horizon in Somersetshire. 



Foreign Distribution. — In the Middle Lias of Trance at Saint Amand, Cher ; at 

 Atys and at Maltol, near Caen, Calvados; Venarey, near Semur, Cote-d'Or; near 

 Avallon, Yonne ; Saint Fortunat, La Pointe d'Orchex, Rhone ; Somme-Thonne, Luxem- 

 bourg. 



Germany, Middle Lias, Kalilefeld ; in Svi^abia it is associated with Aeg. Ibex and 

 Aeg. Maugenesti, as near Cheltenham. A beautiful specimen (PI. LXIX, figs. 2, 3, 4) 

 from the Middle Lias of Wiirtembere; is here fi2;ured. 



Aegoceras Maugenesti, d'Orhigny. PI. XXXVII, figs. 1, 2. 



Ammonites Maugenesti, d'Orhigny. Pal. Fran?.; Terr. Jurrass., t. i, p. 25-1, pi. 70, 



1842. 



— Maugenestii, Quenstedt. Cephalopod., p. 99, tab. v, fig. 1, 1849. 



— Maugenesti, Oppel. Mittl. Lias Schwabcns, p. 77, tab. 2, fig. 3, 1853. 



— — Oppel. Jura-Formation, p. 1 GO, 1856. 



— — Von Hauer. Cephalopod. Lias N.-O. Alpen, Denk. Akad. 



Wissen., p. 53, tab. xvi, figs. 7 — 9, 1856. 

 ■ — Maugenestii, Quenstedt. Der Jura, p. 132, tab. xvi, fig. 5, 1858. 



— Maugenesti, Bumortier. Depots Jurass. du Rhone, vol. iii, p. 69, 1869. 



— — Seebach. Hannov. Jura, p. 82, 1864. 



— — Emerson. Lias von Markoldendorf, Zeit. Deut. geol., 



p. 311, 1870. 



Diagnosis. — Shell discoidal, depressed, sub-carinate ; whorls slightly involute, com- 

 pressed, and flattened on the sides, which are ornamented with from twenty to twenty- 

 four distant equal-sized ribs, straight, erect, and terminating in a row of tubercles at the 

 outer margin of the siphonal area, which is wide, obtuse, and angulated. 



Dimensions. — Transverse diameter 58 millimetres; width of umbilicus 28 milli- 

 metres; height of the aperture 20 millimetres; width of ditto 18 millimetres. 



Description. — The shell of the species very much resembles that oi Aeg. Valdani ; 



