180 Annals of the South African Museum. 



about the middle of the flank, and from here the whorl narrows very 

 gradually towards the periphery, which forms a relatively broad, 

 flattened arch. 



The surface is ornamented with closely set, delicate, linear trans- 

 verse ribs, which have a very slight forward inclination when traced 

 from the umbilicus towards the periphery. On a portion of the last 

 whorl which measures 9 mm. from the umbilical centre to the 

 periphery, there are 12 ribs crowded into a space of 2 mm. at the 

 middle of the flank. There are no constrictions. 



The specimen is imperfect, and is wholly septate. The course of 

 the lobe-line is relatively complex in its details. The siphonal 

 (external) lobe is narrow and very deep, and the small siphonal 

 saddle at its termination narrows somewhat abruptly to a sharply 

 pointed summit. The siphonal lobe is as deep as the first lateral 

 lobe. 



Dimensions. 



Greatest diameter, if completed, about 30 mm. 



Greatest breadth of the last whorl in cross-section 16 ,, 

 Height of the last whorl at the centre, in section... 13 ,, 

 Occurrence. Found in the kloof behind Colchester, Sunday's 

 Eiver Valley, in the middle beds (3h). 



Remarks. This specimen, so far as I am aware, is the only repre- 

 sentative of the genus Phylloceras which has been found in the 

 Uitenhage Series. It is, unfortunately, not a complete individual ; 

 the body- chamber is absent, and a portion of the last whorl pre- 

 served is also broken away. The surface ornaments are only pre- 

 served in a few small patches on the early part of the last whorl, 

 where the outer surface has escaped destruction. In the remaining 

 portions of the surface which are exposed, sufficient of the shell 

 substance is present to prevent the septal suture-line from being 

 seen. It has, therefore, been necessary to etch away part of the 

 shell with acid in order to obtain a view of the suture-line, but owing 

 to the mode of preservation of the cast, the picture obtained is not 

 so satisfactory or complete as might be desired. 



It has been possible, however, to trace the course of the lobe-line 

 so far as concerns the siphonal lobe, the first lateral saddle and the 

 first lateral lobe. The most striking feature is the depth of the 

 siphonal lobe, which touches a radius which is reached by the first 

 lateral lobe. In other respects the lobe-line, so far as observed, very 

 much resembles that given by d'Orbigny in the case of his Ammonites 

 picturatus,* .from the Lower Neocomian of France ; although both 

 * d'Orbigny (1), p. 178, pi. liv., figs. 4-6 (1841). 



