58 PROCEEDINGS COTTESWOLD CLUB 1907 
Remarks :—In the Musée d’Histoire Naturelle (Jardin 
des Plantes), Paris, I saw a specimen of causoniana 
labelled “type, d’Orbigny collection.” It is a form of the 
C. cor-series with thickened margin; but during my 
hurried visit I had not the opportunity of handling the 
specimen. There must be, however, from the localities 
which d’Orbigny cites, a whole series of types ; so that this 
specimen can only be a syntype. 
22, GINCTA ‘sp. 
1884. Waldheimia cor ? Davidson, non Valenciennes 
(Lamarck), App. to Suppl. Pl. xix, fig. 16. 
Remarks :—This stout, short form has not the cordate 
shape of C. cor, nor does it agree with any of the 
examples now figured. It is nearest to C. dives; but 
is shorter and bilobate at a smaller size. It is possibly an 
accelerated development of C. dzves. I have not seen the 
figured specimen, nor have I observed any other like it. 
23. CINCTA sp. 
There is in the British Museum (Nat. History) No. 
67698* from the Etheridge collection, from Radstock, 
a very fine specimen, which looks as if it might be a 
hybrid between C. zzmmosa and C. ds. It has the thin 
form of C. xummosa, but its contour is that of C. ds. It 
is, however, much larger than any specimen of C. ds that 
has yet been noted. 
Development. 
The stages in the phylogenetic development of the 
forms of Czzcta can now be seen by putting together the 
ontogeny of various species which have been described. 
The first stage would have been an elongate or somewhat 
triangular shell like Orvuzthella sarthacenszs, VOrbigny sp. 
(young C. cor) This developed, anteriorly, transverse 
