BIVALVIA. 271 
Panpora optusa. Desh. 2d ed. Lamarck, tom. vi, p. 145, No. 2. 
~ oe G. B. Sowerby. Spec. Conch. (Pand.), p. 2, figs. 1—3. 
— — Phil. En. Moll. Sic., vol. ii, p. 14, t. 13, fig. 13. 
— — Forb. and Hanl. Hist. Brit. Moll., vol. i, p. 210, pl. 8, fig. 5; and 
pl. G, fig. 10, animal. 
TRUTINA SOLENOIDEA. Brown. Illust. Brit. Conch., pl. 13, fig. 5, 1827. 
Spec. Char. Testa obtusé-elongata; latere postico versus extremitatem dilatato; margine 
dorsali planiusculo. 
Shell obtusely elongate ; posterior side dilated towards the extremity; dorsal margin 
nearly straight. 
Length, inch. Height, % inch. 
Locality. Red Crag, Walton Naze. 
Only two or three specimens of this species have fallen under my observation, and 
I have, in deference to the malacologists, separated this from what is called rostrata. 
Colonel Montague, who, notwithstanding his having described the two shells under 
different generic names, was afterwards of opinion that the one was only the younger 
state of the other. Messrs. Forbes and Hanley consider the characters of the animal, 
as well as those of the shell, to be quite distinct, and have kept the two forms 
separate. My own specimens are not sufficiently numerous or perfect to assist in 
the determination. ‘The two shells are so much alike in the young state as to be with 
difficulty determinable; and I am inclined to believe with Montague, so far at least in 
their specific identity, that if the one be not exactly the young state of the other, there 
is not more than a local variation between the two. Both appear to have existed 
during the Crag Periods, the rostrata in the Cor. Crag corresponding with the more 
_ Southern form, while that from the Red Crag resembles the Northern one (probably 
P. glacialis, Leach, ‘ An. Phil.,’ vol. xiv, p. 203, 1819). 
Ne#ra,* J. £. Gray, 1830. 
AnatiNa (sp.) Lamk. | Erycina (sp.) Risso, 1826. 
Corsuta (sp.) Desh. 1835. Cuspiparia. Nardo, 1840. 
Turacta (sp.) Brown, 1827. | 
Generic Character. ‘‘ Shell transversely ovato-pyriform, inequivalve, inequilateral, 
more or less beaked, and gaping posteriorly; surface smooth or striated, or ribbed 
longitudinally, never punctated, with or without an epidermis; valves strengthened 
internally with a longitudinal rib; hinge composed of a cartilage fulcrum, usually 
oblique, and spatulate in each valve, sometimes with a minute tooth beside it, and a 
more or less developed lateral tooth on the rostral side of one or both valves; ligament 
external (?), small; muscular impressions large, pallial with a very shallow sinus. 
* Etym. (?) Neawa, proper name. This is also employed for a genus of insects. 
