558 ON A GIGANTIC EXTINCT SPECIES OJ? MYLIOBATIS. [Juue 20, 



connecting the two. A broad streak of orange colour extends 

 along the inner margin. 



The underside of the body is similar to R. Jceithloa, but on the 

 upper surface the head and thorax are a bright blue-green, with the 

 body dark bro\A'n. 



Hab. Angolares. 



Expanse 2| inches. 



Pteeygospidea elesus. 



Tagiades jlesus (Fabr.) ; Kirby, Syn. Cat, Diurn. Lepid. p. 635. 



Paenara niso. 



Parnara niso (Linn.) ; Kirby, Syn. Cat. Diurn. Lepid. p, 597. 



3. On the Dentition of a Gigantic Extinct Species of 

 Myliobatis from the Lower Tertiary Formation of 

 Egypt. By A. Smith Woodward, F.Z.S. 

 [Eeceived June 20, 1893.] 

 (Plate XLVIII.) 



The Skates of the family of Myliobatidse are well known to 

 attain a great size, but few examples even of the dentition of the 

 largest specimens are preserved in museums. It is therefore of 

 much interest to record that the British Museum has lately 

 received from Surgeon-Captain E. H. Penton a good example of 

 the jaws of one of the most gigantic extinct species of Myliobatis, 

 discovered in the Lower Tertiary Limestone of the Mokattam 

 Hills, near Cairo, Egypt. So far as the present writer is aware, 

 this is the largest specimen of the dentition of Myliobatis that has 

 hitherto reached any museum. 



Each jaw is in a separate piece of limestone, but the two portions 

 are known to have been found in association ; and, as usual in the 

 Myliobatida^, one dentition (lower) is flat, while the other (upper) 

 is much bent from front to back. Of the lower jaw, partly shown 

 in the figure (Plate XLVIII. fig. 2), about 17 series of plates are 

 preserved, 10 being worn ; while of the upper jaw (fig. 1 ) only 6 

 series remain. The unworn teeth are almost smooth, being marked 

 only by short feeble longitudinal striae or rugae. In both jaws the 

 oral surface is arched from side to side, very gently in the lower, 

 more strongly in the upper jaw, as well shown in the sections 

 figs, la, 2 a. The principal teeth are very slightly arcuated and 

 not strongly reflexed at the extremities ; and the narrow lateral 

 teeth have their long axes directly antero-posterior, not oblique. 

 As an abnormality, it is also interesting to note in the upper den- 

 tition that the two outer lateral series are fused together on one 

 side, while the two inner lateral series are similarly fused on the 

 other side. 



