OSTREA. ews 
A change perchance occurred in the ‘ Museum Ulrice,’ where 
the same engraving is again referred to, yet the details men- 
tioned do not precisely agree with the language of Gualtier, 
whose “ex fusco viridescens” does not exactly harmonise with 
the “ flavo-testacea”’ of our author: colour, however, is often a 
varietal distinction only. The byssal aperture is somewhat 
awkwardly described; yet the meaning is intelligible from the 
language used for the same part in the account of O. margariti- 
fera, and from the cited engraving. 
When Linneus at first described the species, he did not 
himself possess it: in the interleaved copy of his twelfth 
edition, which he was revising for a thirteenth edition, its 
presence in his private cabinet is asserted. I fear, however, 
from the “ cardo ut sequentibus” of his manuscript that he had 
forgotten his own borrowed type. It was possibly from having 
read the Linnean manuscript that Solander considered semi- 
aurita to be a mere variety of the succeeding Perna: Grono- 
vius most unreasonably has cited Seba’s delineations of some 
forms of P. isognomon in illustration of the Linnean species. 
I find no specimen in the collection marked for the species, 
nor do I observe any either that strictly answers to the require- 
ments of the definition. ‘The nearest approach to the ideal of 
the ‘Museum Ulric’ seems the Perna sulcata; but the “levi” 
is opposed to such an identification. There is likewise a 
beautiful little Avicula intermediate in aspect between the 
Mytilus ala-corvi (suggested by Morch for O. seniaurita) and 
meleagridis of Chemnitz, that is not so unlike the few words of 
the ‘Systema,’ and the figure * in Gualtier. 
Ostrea pera. 
This species, which only appeared in the twelfth edition of 
the ‘Systema,’ was eventually designed by Linneus, as the 
“gen. nov.” of his revised copy of that work manifests, to have 
constituted a new genus along with the last and the succeeding 
* In the Vienna reprint of the twelfth edition, the 84 was erroneously 
misprinted 48. 
