218 Annals of the South African Museum. 



similar. M . rapax, however, attained much larger dimensions and 

 more robust form than any of the specimens of M. sclnvarzi 

 examined, and it appears also from Dr. Harbort's figures that the 

 cephalothorax of his species has less relative lateral compression. 

 Other differences that may be noticed are as follows. In M. rapax 

 the development of the obliquely running blunt branchial keel is 

 much more pronounced ; the anterior margins of the abdominal 

 pleura are denticulated ; the sixth abdominal segment has greater 

 lateral depth and is not so depressed dorsally as the corresponding 

 segment in M. schtuarzi. Further, Dr. Harbort makes no mention 

 of distinctive ornaments on the telson such as those which charac- 

 terise the African form. The little smooth oval area at the anterior 

 end of the branchial groove, which is well marked in M. schwarzi, 

 does not appear to be an evident feature in M. rapax, if developed 

 at all, and the same may be said of the grooves of attenuated 

 sigmoidal form in front of the cardiac region of the carapace. 



With reference to the above-mentioned small, smooth, oval area, 

 which is situated on either side of the carapace on the anterior part 

 of the branchiostegite, this structure is well represented also in 

 Mcyeria magna M'Coy, but does not seem to have attracted special 

 attention. Its significance is not obvious, but it appears to be 

 homologous with the similar areas on the carapace of Pseudo- 

 glyplicea. These were considered by Oppel to be a constant 

 characteristic of that genus,* and he referred to them as " reni- 

 form eminences," but did not enter into the question of their 

 meaning. Corresponding structures of modified form may also be 

 seen in some species of Glypliaa. 



(A). LISTS OF THE FOSSILS CRITICALLY EXAMINED. 



The lists of fossils collected by Messrs. Eogers and Schwarz in 

 1900 and by Mr. Eogers in 1905 should be read in connection with 

 the published official reports by these authors, which contain the 

 records of additional forms seen by the Surveyors to occur at some 

 of the localities. Thus, for instance, in the first report, among the 

 fossils stated to have been found in the Marine Beds at Grass Eidge, 

 near Uitenhage, there are the names of ten Mollusca, specimens of 

 which were not brought away. I In the later report by Mr. Eogers, 

 many fossils are in like manner recorded, which are not represented 

 in the collections submitted for examination. | 



* Oppel (1), p. 51. f Rogers and Schwarz (1), p. 9. J Rogers (2). 



