The Invertebrate Fauna of the Uitenhage Series. 95 



except their state of preservation by which they may be dis- 

 tinguished from those occurring in South Africa."'" Having due 

 regard to the range of individual variation shown by the specimens 

 which occur in the Oomia beds, I believed this statement to be 

 quite accurate, but a reconsideration of this matter and a renewed 

 comparison between a larger number of specimens now necessitates 

 a slight modification. While it is seen that the limits of individual 

 variation among the Indian specimens cover differences greater 

 than those to be observed between the average characters shown 

 by examples of the species from the one region and those from the 

 other, it should be noted that in India many of these shells exhibit 

 a somewhat less degree of inflation than that seen in most of the 

 South African examples. The specimens from Cutch sometimes 

 have the tubercular ornaments rather more prominently developed, 

 though in certain cases the effect of prominence seems to have 

 been enhanced by the mode of preservation of the shells. There 

 is also a tendency to have the tubercles less closely crowded 

 together and less regularly moniliform than in the specimens from 

 South Africa. It is difficult to say in how far these characters 

 may have been the product of strictly local conditions. There 

 certainly appears to have been a greater range of individual varia- 

 tion and greater instability than is shown by the specimens from 

 the Uitenhage beds. At the same time, the agreement between a 

 selected series of specimens from the one region and a suite of 

 individuals from the other is remarkably close, and, all things 

 considered, I do not think that the points of difference, above 

 noted, suffice for the establishment of two separate species, or, 

 indeed, even for the satisfactory recognition of two well-defined 

 local races. 



TKIGONIA KRAUSSI sp. nov. 

 Plate III., figs. 2, 2a. 



1850. Lyrodon ventricosus F. Krauss (partwi), Nov. Act. Acad. Caes. 



Leop.-Carol. Nat. Cur., vol. xxiL, pt. 2, Tab. 49, figs. 2a, 



2b (exclude figs. 2c-2/). 



Description. The shell is relatively short, anteriorly very high, 

 with the upper and lower margins rapidly converging posteriorly 

 towards the very short siphonal margin. The valves are anteriorly 

 very strongly inflated, but posteriorly compressed. The umbones 

 are prominent, strongly incurved and markedly recurved, and 

 situated close to the anterior end. The greatest height is attained 



* Kitchin (1), p. 107. 



