AEGOCERAS SAGITTARIUM. 355 



the finest examples known have been obtained from the Middle Lias at Hechingen, 

 Wiirtemberg ; these examples are identical with the Pabba types, one of which is figured 

 on PI. XI, figs. 4 — 6, and a second on PI. LI, fig. 3. I have found only two fragments 

 of a large shell in the Cheltenham beds, and both specimens belonged to the true Pabba 

 type. 



Locality and Stratigraphical Position. — Aegoceras Jamesoni is a leading fossil of the 

 zone which it so well characterizes. It is found near Cheltenham, Gloucestershire ; Eenny- 

 Compton, Warwickshire ; Hunger, Somerset ; Charmouth, Dorset ; Robin Hood's Bay, 

 Yorkshire ; and in the islands of Mull and Pabba in the Hebrides. 



Foreign Distribution. — In Prance it has been collected at Coutards and Bois-de- 

 Trousse, near St. Amand, Cher ; Sachi, Ardennes, Evrecy, Calvados ; St. Rambert, Ain ; 

 near Lyons, Rhone. 



In North-west Germany it has been found near Rottorf, Roklum, Hedeper, Harz- 

 burg, Liebenburg, Bodeustein, Kahlefeld, Willershausen, Oldershausen, Markoldendorf, 

 Palkenhagen, and other localities. In South Germany it is found in Swabia in many 

 localities, as at Pliensbach, near Boll, Soldelfingen, Hechingen, Balingen, &c. ; in all the 

 localities it occupies the same horizon, namely, at the base of the Middle Lias. 



Aec/oceras SAGITTARIUM, Blake. PI. LIL figs. 1 — 5 ; PI. LIIa, figs. 1 — 6. 



Ammonites Jamesoni, Simpson. Foss. York. Lias, p. 48, 1855. 



Aegoceeas SAGITTARIUM, Tate and Blake. Yorkshire Lias, p. 2/6, pi. vii, fig. 2, 

 1876. 



Diagnosis. — Shell discoidal, compressed: volutions five, uniformly rounded, and one- 

 fourth involute ; outer whorl one third the diameter in height with twenty -two to twenty- 

 six slightly bent ribs moderately elevated, rounded, and disappearing near the margin 

 of the siphonal area, which is in general smooth and convex, but sometimes has an 

 elevated ridge which occupies the mesial line, and passes longitudinally round the shell ; 

 aperture oblong, narrower in the outer half. 



Bi7nensions — Small specimens. — PI. LII, fig. 4. Transverse diameter 56 millimetres; 

 width of umbilicus 25 millimetres; height of last whorl 19 millimetres; height of 

 aperture 18 millimetres; width 17 millimetres. 



Large specimen. — PL LII, figs. 1, 2. Transverse diameter 240 millimetres ; width of 

 umbilicus 95 millimetres ; height of last whorl 90 millimetres ; width 50 millimetres. 



Description. — This shell has been long known to me as a Yorkshire variety of Aego- 

 ceras Jamesoni, which I had separated from my Pabba types under a distinct diagnosis ; 

 now that Professor Blake has figured this form in his Yorkshire Lias under a specific 

 name, priority of publication entitles him to precedence. I am indebted to the 



