The Invertebrate Fauna of the Uitenhage Series. 217 



side. The usual condition of the abdomen is one of flexion, with the 

 pleura overlapping one another in a marked degree ; but one of the 

 specimens examined (38h) shows segments iii.-vi. so extended 

 that the form of the pleura is well exhibited. It will be noted that 

 the conventional terminology here used in reference to the main 

 divisions of the body is that which is most widely known and 

 employed. 



The transverse grooves on the terga of the abdominal segments 

 mark the degree of overlap of the segments when these are in the 

 position of extension. The grooves probably correspond with 

 strengthening ridges on the interior surface of the terga which 

 pass upwards from the ball (anterior) and socket (posterior), respec- 

 tively, of the lateral articulations in each segment. The depth and 

 the dorsal continuity of the anterior groove in the sixth segment, and 

 the smooth, convex, well-developed rolling facet anteriorly to it, 

 which fits closely under the hinder part of the fifth tergum, appear 

 to be contrivances for securing the rigidity and strength called for 

 in the exercise of rapid and vigorous movements of the tail in swim- 

 ming or springing. The tergal facets of the preceding segments are 

 much less well developed and defined. 



Meyeria schwarzi differs widely from M. ornata (Phill.)," from the 

 Speeton Clay, in the absence of the characteristic ornaments on the 

 abdominal terga and in the form of the pleura, as well as in other 

 features. From M. magna M'Coy [= M. vectensis Bell],t of the 

 Aptian of the Isle of Wight, it is readily separable by the absence of 

 ornamenting granular ridges on the abdominal terga, by the weaker 

 development and different position of the oblique branchial fold or 

 carina, and by the form of the pleura. M. magna also appears to 

 be a much larger and more robustly formed species. It may 

 be remarked that the fragment of an elongated ambulatory leg 

 (South African Museum collection, No. 663), mentioned above, bears 

 much resemblance, in its relative proportions and in its tuberculated 

 ornamenting keels, to the long and slender anterior thoracic legs of 

 M. magna.\ 



There appears to be very considerable resemblance between 

 M. schwarzi and M. rapax Harbort, from the Lower Valanginian 

 of North Germany. Both have a smooth surface in the abdominal 

 terga i.-v., and the form and ornamentation of the pleura are very 



* Bell (1), p. 33, pi. ix., figs. 9-11. 



f M'Coy (1), p. 334 ; Bell (1), p. 33, pi. x. 



I Bell (1), pi. x., figs. 1, 4. 



Harbort (1), p. 11, Taf. i., fig. 12 ; ii., figs. 1-4 ; iii., figs. 1, 2 ; xi., figs. 1, 2. 



