Dr. J. E. Gray on the Names of the Genus Mystomys. 425 



27. Primitia muta, nov. 

 Cytheropsis concinnal, ibid. p. 254, pi. 9. fig. 3. 

 Oblong- ovate, nearly Leperdiiia-shaped ; back straight, ends 

 rounded but unequal; ventral edge convex; surface smooth. 

 Though resembling P. concinna at first sight, it is less cylin- 

 drical, broader at the obliquely rounded end, and its ventral 

 dge is more symmetrically curved : it is near to P. rugulifera in 

 shape. From the Upper Silurian Limestone of Beech ey Island, 

 with P. rugulifera, P. sigillata, Beyrichia clathrata, B. plagosa, 

 and Leperditia gibbera. 



EXPLANATION OF PLATE XIIL 



[The figures are magnified about 20 diameters.] 



Fig.\. Primitia cristata, J. & H. : a, carapace, view of right valve; 



b, posterior view ; c, dorsal view. 



Fig. 2. P. umbilicata, J. & H. : a, left side of carapace; b, dorsal view ; 



c, ventral view ; d, insi-le of valve (filled with matrix). 



Fig. 3. P. tersa, J. & H. : a, carapace, side view; b, dorsal view; c, ven- 

 tral view. 



Fig. 4. P. trigonalis, J. & H. : a, carapace, view of left valve ; b, dorsal 

 view. 



Fig. 5. P. renulina, J. & H. : a, carapace, side view; b, dorsal view. 



Fig. 6. P. variolata, J. & H. : a, left valve; 6, its edge-view; c, right 

 valve of var. paucipunctata ; d, its edge view. 



Fig. 7- P. matutina, J. & H. : a, right valve ; b, its edge view. 



Fig. 8. P. Roemeriana, J. & 11. : a, carapace, side view (left valve); b, pro- 

 file. 



Fig. 9. P. Beyriehiana, J. & H., right valve. 



Fig. 10. P. semicircularis, J. & H. ; a, left valve; b, its end view ; c, ven- 

 tral edge. 



Fig. 11. P. pusilla, J. & H. : a, right valve ; b, its edge view. 



Fig. 12. P. obsoleta, J. & H. : a, right valve ; b, its end view ; c, edge 

 view (ventral). 



Fig. 13. P, ovata, J. & II. : a, right valve; b, its end view; c, edge view 

 (ventral). 



Fig. 14. P. oblonga, J. & H. : a, right (?) valve; b, its end view; c, edge 

 view (ventral). 



XLVIII. — On the Names of the Genus Mystomys. (In a Letter 

 to Professor Allraan.) By Dr. J. E. Gray, F.R.S., V.P.Z.S., 

 F.L.S. &c. 



British Museum, Nov. 15, 1865. 

 Dear Professor Allman, 



As I have been informed that, in your paper on the animal 

 that Du Chaillu noticed as Cxjnogale velox^ you persist in retain- 

 ing the generic name of Putamogale, I venture to send you the 

 following observations, in the hope that I may induce you to re- 

 consider the question, and avoid adding another to the several 

 useless names which the animal has already received. 



