LUDWIGIA, SP. 107 



Ludwigia, sp. Plate XXIII, figs. 9, 10. 



1874. Ammonites Escheei, Vumortier (non von Hauer). Etudes pal. Bassin 



Rhone, pt. iv, pi. xix, fig. 7. 



This is the only specimen of this species which I have seen, and so I refrain 

 from giving it a name, especially as it is not well preserved. Apparently, 

 however, the same species was figured by Dumortier under the name " Am. 

 Esckeri, von Hauer," and this circumstance directed my attention to this 

 specimen. It differs, however, in many respects from von Hauer's figure of his 

 species, and notably in the absence of all ventral furrows. I fancy that 

 Dumortier' s figure does not represent von Hauer's species ; but unfortunately, as 

 Dumortier gives no front view of his specimen, there must be some doubt as 

 regards the agreement of our specimen with his as to the ventral area. In the 

 lateral area the resemblance is very complete ; and both differ from von Hauer's 

 figure. 



To me it seems very probable that this species may be the ancestor of the 

 dwarf Ludwigice (L. costosa, cornu, fyc). In general shape it resembles them 

 entirely, while it differs only in having obscure knobs on the inner area instead of 

 ribs ; and such ornamentation would point to a lower degree of development, 1 

 which is exactly what might be expected. 



Its geological position harmonizes with this theory, since it comes from the 

 base of the Cotteswold Sands ( Variabilis-suhzone) at Nailsworth, Gloucestershire. 

 It was collected by the late Mr. E. Witchell, and has been very kindly lent by his 

 family to be figured in this work. More specimens are desirable. 



Ludwigia, sp. Plate XXIII, figs. 2 — 4. 



This species appears to be intermediate between Li/Ma and Ludwigia, since it 

 has retained the ventral furrows of the former genus, while its ornamentation is 

 that of the latter. 



We must not lay too much stress upon the occurrence of forms, like this and 

 the last, apparently transitional between two genera, especially when they are so 

 small and the material so insufficient. If, when more specimens are obtained, 

 these species are seen to be really transitional, they might be conveniently 

 designated by combining the two generic names, as, for instance, Lillia- 

 Ludwigia* sp. (the parent genus first), which would exactly state their relation- 



1 See next page. 



2 If species represent the steps in evolution genera may be likened to the flights of steps. I have 

 no wish to combine the generic names Ludwigia and Lillia, except in such circumstances as above, nor 



