ARCA. 97 
the older writers, is not admitted as its analogue by the more 
original Bruguiére, who at the same time acknowledges that he 
had never met with a specimen that precisely corresponded with 
its described features. The species designed by Schréter is by 
no means clear; indeed, no notice is taken of it in Reeve’s 
Monograph of the Pectunculi. It is a beautifully streaked and 
clouded bivalve, which reminds us of P. pennaceus, lineatus, 
glycimeris, &c., with the arrangement of its teeth peculiarly 
arched, circumstances by no means suitable to the pallid 
shell, with almost transversely disposed teeth, specified in 
the ‘Museum Ulrice.’ I should prefer, as a mere surmise, 
to suggest the possibility of the Linnean 4A. pallens proving 
identical with the Pect. violascens* of the Mediterranean, yet 
the positive recognition of the species must be based upon an 
examination of the type in the Dronningen Museum. 
Arca wndata. 
The type of this shell is still preserved in the Linnean 
cabinet, marked with the numerals indicative of its identity 
with the Arca wndata, and according with the published 
description of that species. It is an ill-preserved specimen 
of the Pectunculus lineatus (Reeve, Conch. Icon. vol. i. 
Pect. f. 25), with shape and surface so marvellously altered by 
attrition as to have rendered any descriptive portraiture (should 
fuller details have been attempted) a mere source of error: the 
name wndata cannot then take precedence over the later appel- 
lation. 
So closely do examples of decussatus resemble lineatus in 
general aspect, that one naturally feels surprised at the specific 
separation of such allied forms by our author. His sectional 
arrangement of the Arce by the position of their beaks, 
accounts, however, for the circumstance; since the former 
species falls into the division with recurved beaks, the latter 
becomes necessarily associated with such as have their beaks 
* Since writing the above paragraph, I find that Morch, likewise, has 
arrived at a similar conclusion. 
O 
