328 Annals of the South African Museum. 



"The valves are sub-oval ; the beak is anterior and not prominent. 

 The dorsal border is almost straight. The anterior border is rounded 

 and passes insensibly into the ventral border, with which it forms 

 a very regular curve. The ventral border is regularly convex ; it 

 joins the posterior border, which is oblique to the dorsal border, by 

 a very obtuse angle. The valves carry about fourteen concentric 

 ribs. The state of preservation does not permit of the presence of 

 an intercostal ornamentation being stated." 



Leriche states that these fossils belong to a group of "Estheria" 

 characterised by a regular concentric ornamentation formed of pro- 

 minent spaced ribs. This group has been called Euestheria by Deperet 

 and Mazeran. The Congo form approaches most closely E. manga- 

 lensis but is distinguished by the slightly more elongate shape and 

 the sharper demarcation of the posterior and ventral borders. E. greyi 

 has a similar ornamentation but has a more oval and more inequi- 

 lateral form. 



Specific identification is not possible without a knowledge of the 

 intercostal ornamentation. 



FAM. APODIDAE. 



LKPIDURUS, Leach. 



LEPIDURUS STORMBERGENSIS sp. nov. 



This form is represented in the South African Museum collection 

 by a number of impressions on shale. Some represent isolated 

 carapaces of immature animals; others more or less complete mature 

 individuals. No specimen is perfect, and therefore several have been 

 examined in the preparation of the following description. In some 

 cases impressions of the appendages are fairly well-preserved, but 

 detailed description of these is postponed. 



The carapace is almost circular, slightly longer than broad, and 

 deeply emarginate behind, the emarginate portion having an untoothed 

 border. There is a strong median keel extending from the hinder- 

 border to a short distance behind the eyes. 



Measurements of four carapaces of varying size are as follows: 



Median length Maximum length Maximum breadth 

 9 mm. 10'3 mm. 10 mm. 



9 mm. 11 mm. 10 mm. 



11 mm. 13 mm. 12 mm. 



19 mm. 17-5 mm. 



