480 THE LIAS AMMONITES. 



Locality and Stratigraphical 'Position. — I collected three specimens of this shell many 

 years ago from the Upper Lias clay at Stinchcombe Hill. I also obtained one small 

 tolerably perfect specimen from the Upper Lias sands at Nailsworth. The species 

 appears to be rare in Gloucestershire, seeing that I have never met with it in other 

 collections. 



Stephanocebas Braunianum. d'Orhigny. PI. LXXXVI, figs. 3, 4; PI. LXXXVII, 



figs. 5, 6. 



Ammonites Beaunianus, d'Orhigny. Paleont. Fr., Terr. Jurass., t. 104, 



fig. 3, 1842. 

 — — Chapuis et Bewalgue. Mem. Cour. Acad. Roy. 



Belgique, t. xxv (Foss. 

 du Luxembourg) pis. vi 

 and vii, fig. 2, 1854. 

 Stephanocekas Braunianum, Tate and Blake. Yorkshire Lias, p. 300, 1876. 



Diagnosis. — Shell discoidal, compressed ; area round, flat ; whorls quadrate, slightly 

 involute, transversely costated ; costae thirty-six to forty, straight, simple, approximate, 

 externally mucronated near the margin, and bifurcated over the area.- 



Dimensions. — Transverse diameter 35 millimetres; height of last whorl 12 milli- 

 metres; width of umbilicus 18 millimetres; height of aperture 10 millimetres; width 

 (S)f aperture 12 milHmetres. 



Description. — The shell of this species has a neat quadrate form, the outer whorl, 

 is slightly involute, flat on the sides, which are covered with thirty-six straight, simple, 

 acute ribs, which terminate in a point situated at the angle of the siphonal area ; here 

 the rib bifurcates, the two smaller costse pass over the flat area and both form a curvature 

 the convexity of which is directed forward. The siphonal area is flat and convex, pro- 

 vided with twice as many costse as are seen on the sides. The spire is composed of 

 depressed subquadrate whorls, which are only slightly involute. The section of the 

 aperture is subquadrate, and slightly grooved by the return of the spire. 



Neither of my specimens exhibit the suture-line. In PI. LXXXVI, figs. 3, 4, I 

 have figured a very perfect small example of this species (magnified 2^ diameters) which 

 displays the structure of the test very well. 



Acuities and Differences. — In its general form it somewhat resembles Stephanoceras 

 commune, but it difiiers from that species in possessing sharp prominent tubercles at the 

 angle of the area, in the whorls being less in number, and in the costse being coarser. 



Locality and Stratigraphical Position. — My two specimens were both collected from 

 lower sands at Nailsworth belonging to the upper portion of the Lytoceras Jurense 

 bed, which is well developed there. 



