152 SPECIES OF THE SYSTEMA. 
it should have been for that species, but “ab apice extrorsum 
rotundatus” (rounded off from the extremity ventrally,* as ex- 
hibited in the P. bicolor of Chemnitz, and the cited figure (pl. 
79, C.) of Gualtier. The latter, apparently the sole source of 
the irrecognisable P. bullata of Gmelin, has been likewise 
quoted by Lamarck for his P. marginata, and the few charac- 
ters mentioned by that naturalist are not inharmonious with 
the description of rotundata in the ‘Museum Ulrice. Unfor- 
tunately, however, I have not succeeded in discovering a Pinna 
in our English cabinets which exactly answers to the La- 
marckian definition. 
Our author has neither recorded his possession of this spe- 
cies nor has enlarged his former insufficient description by any 
manuscript additions. Hence, although the young of several 
kinds of Pinne, with some of their scales abraded, would fairly, 
and alike, correspond to the ideal of the Linnean rotwndata, no 
certainty can be arrived at, unless the type should be still pre- 
served in the Dronningen Museum. 
Btuwa saccata, 
Few species have been better defined by our author than his 
Pinna saccata. The figures referred to harmonise with the de- 
scription of the shell in the ‘Museum Ulrice, which is suffi- 
ciently ample and peculiar (“ teste sutura dorsali coadunatz”’) 
to ensure recognition. Chemnitz only failed to identify it from 
not having met with a mature example: his vitrea is supposed 
to be the fry of it. The Pinna saccata of Lamarck (Leach, 
Zool. Miscell. vol. i. pl. 51) is clearly identical; and of this a 
specimen, the sole one in the cabinet which suits the defini- 
tion, is still preserved in the Linnean collection. 
Pinna Vigtttformts., 
Our author did not himself possess this species, but referred 
to the ‘Museum Ulric’ even before that work had been pub- 
* The outer or gaping side. 
