Miscellaneous. 69 



sexual differentiation ; another (P. Mahadeva) in which, while 

 agreeing in structure, they differ to a considerable extent in mark- 

 ings and colour, and the secondary sexual characters of the male 

 are much more pronounced ; another (P. Castor) in which they 

 differ from one another to such a remarkable extent, that no 

 less an authority than Prof. Westwood originally described them 

 under different names, and still maintains their distinctness, and 

 Mr. Wallace* placed them in different groups of the genus — the 

 male having acquired the most pronounced secondary sexual cha- 

 racters (including rudimentary tails), which have been partially 

 transmitted to some females but not to others, and the two forms 

 of female having retained, one of them the form of wings, and both 

 the general style of colouring, characteristic of both sexes in the 

 first-named species; and, finally, others (P. Ilelenus, P. Chaon, &c.) 

 in which the male has perfectly transmitted to the opposite sex all 

 the secondary sexual characters (including the long tails) that lie 

 had acquired, the female only differing from him in such trifling 

 points as the lighter coloration of the outer half of both wings and 

 the dingier shade of the upper surface generally. 



From these and other facts, we are, I think, entitled to infer the 

 probable descent of all the members of this group from an ancestor 

 with tailless, rounded wings in both sexes, closely resembling P. 

 Dravidarum, but with diffused discal markings in the hind wings, 

 and probably also in the fore wings — the conspicuous wing-blotches 

 of P. Uehnus, P. Castor, &c. having apparently resulted from the 

 concentration, so to speak, of such diffused colouring in the direction 

 of the breadth of the wing, just as have the discal bands of short 

 spots in P. Dravidarum and P. Mahadeva from a similar process of 

 modification in the oi^posite direction. 



If his conclusions are correctly reported. Prof. Westwood's draw- 

 ings must represent a species different from either of those alluded 

 to herein ; and I look forward with much interest to the appearance 

 of his paper. — Proc. As. Sac. Beng. 1880, jN^o. 3. 



On a Mgldij organized Reptile from the Permian Formation. 

 By M. A. GAiTDKr. 



M. Roche, director of the Ironworks of Igornay, to whom we are 

 already indebted for several discoveries of curious fossils, has just 

 found, in the Permian, a new genus of reptile, which he has pre- 

 sented to the Museum of Paris. The Igorna)' animal is the most 

 perfect of those which have hitherto been met with in the Pri- 

 mary formations of France. I propose to name it Stereorachis 

 dominans. 



In Stereorachis the vertebrae present a striking contrast to those 

 of the reptiles of the same deposits. While in Actinodon and 



* In his well-known memoir " On the Phenomena of Variation and 

 Geographical Distribution as illustrated by the Papilionidae of the 

 Malayan P»egiou," in Trans. Linn. Soc. Loud. vol. xxv. pp. 33, 34. 



