474 Mr. T. Davidson on the genus Waltonia. 
XLIT.—On the genus Waltonia. By Tuomas Davipson, Esq. 
[With a Plate. ] 
M. Boucuarp and myself, in Jan. 1848*, published a detailed 
description of the genus Magas, Sowerby, with figures illustra- 
ting the internal structure of this remarkable little shell, at that 
period incompletely known. Some time after I wrote a papert 
with figures on a recent species known under the name of Tere- 
bratula rosea, which shell, from the peculiar arrangement of its 
internal organization differing from that of all known Brachio- 
poda, led me to propose for it a distinct generic name, that of 
Bouchardia, belonging to the family of Magaside; Magas pu- 
milus and Bouchardia rosea being the only species in each genus. 
During a late visit to Paris, M. Valenciennes kindly lent me 
specimens of recent Terebratule brought to Europe by Quoy and 
Gaimard ; and on a tablet on which were placed several specimens 
of Terebratula sanguinea, Leach, I found a small shell whose or- 
ganization was completely different from those with which it was 
surrounded, but offering characters not allowimg of its being 
placed in either Magas or Bouchardia, but claiming a new 
generic name, and forming part of the family of Magaside. 
M. D’Orbigny, in his ‘ Pal. Franc. Ter. Crétacés,’ vol. v, p. 52, 
places in this family Magas and Terebratulina ; I cannot however 
agree with that author in this association, as I consider the orga- 
nization of Ter. Caput serpentis to be completely different from 
that of Magas, and not to belong to the same group or family. 
In a very interesting paper by Mr. King { on certain genera of 
Palliobranchiata, the internal organization of Terebratula rosea 
is alluded to; and in the great work by that author on the 
Permian fossils of England, Mr. King has adopted and placed 
in the same family of Magaside the genus Mayas, Sow., and my 
Bouchardia. 
Genus Wattonta. 
Char. Shell bivalve, inequivalved, equilateral, subovate, slightly 
convex ; beak almost straight, partly truncated by a large foramen 
extending from the summit to the umbo of the ventral valve 
which it partly encircles ; deltidium small, disunited, and forming 
only a portion of the peduncular opening : at the base of the beak 
are two strong teeth corresponding with the sockets of the ventral 
valve. The interior of the dorsal valve is simple, with a slight 
central longitudinal elevation dividing the shell into two equal 
portions, not extending quite tothe margin. In the ventral valve 
* Bull. Soc. Géol. de France, vol. v. 2nd series, p. 139, pl. 2. 
+ Ibid. vol. vi. 2nd series, 1849. 
{ Annals and Mag. of Nat. Hist. vol. xvin. 1846. 
ee ai, «eel 
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