The Invertebrate Fauna of the Uitenhage Scries. 133 



points of distinction appear to be constant and to justify the definite 

 separation of these two forms. In the Lincolnshire specimens the 

 shell is as a rule less orbicular, and attains greater height in propor- 

 tion to length ; at the same time, the valve is rather more flattened 

 towards the inferior margin in fully grown individuals. The lunule 

 has greater relative length and is less deeply excavated and less 

 concave in form than in A. hcrzogi. The noticeable fact that the 

 sculpture in the Lincolnshire examples is less well denned than in 

 the African shell may perhaps be in some measure due to the 

 mode of preservation. The form and size of the lunule certainly 

 affords a good separating character, and as regards the outline 

 of the shell, the difference above mentioned seems to hold good 

 if specimens of average proportions be compared, though it must 

 be admitted that Astarte herzogi exhibits considerable shape 

 variation, and specimens with shorter and higher outline occur 

 not infrequently. 



As already remarked, Astarte striata Sow.,* from the Blackdown 

 Beds, agrees in many respects, but it is a much more compressed and 

 flattened shell, has greater length in relation to height, and shows no 

 marginal crenulation. 



Astarte beaumonti Leym.,f from the Neoconiian of the Aube, is 

 likewise characterised by a sharply demarcated and deeply excavated 

 lunule, and is ornamented by ridges and sulcations similar to those 

 of A. herzogi; it may probably agree, too, in the internal characters, 

 but it differs by its inequilateral form and oblique elongation. 



Astarte biichi P. Eoemer I (Lower Cretaceous, Perte du Ehone) 

 seems to agree well in internal characters, though it is not clear 

 whether a posterior lateral tooth of the right valve is plainly 

 developed. The sub-lunular groove in the hinge of the right valve, 

 shown in Eoemer's figure, seems to indicate the presence of an 

 anterior lateral tooth in the left valve. The sharply cut, elongated 

 escutcheon and the well-sunk short lunule are similar, but Eoemer's 

 shell differs from A. herzogi by being considerably more inequilateral 

 in shape and also less incurved at the umbones, besides having much 

 less perfectly developed concentric surface sculpture. 



Astarte samanni de Loriol, from the Portlandian of the north of 

 France and of England, || is more similar again, and may be closely 



* J. de C. Sowerby (1), vol. vi., Tab. 520, fig. 1 (1826). 



f Leymerie (2), p. 4, pi. 4, fig. 1. 



\ F. Boemer (1), p. 20, fig. 4. 



De Loriol and Pellat (1), p. 68, pi. vi., fig. 9. 



|| Blake (l),p. 232, pi. x., fig. 5. 



10 



