16 MOLLUSCA FROM THE GREAT OOLITE. 
to the first, and generally opposite to it, a character rarely if ever found in the recent 
Pterocer or Rostellarie.* 
Avarta arMATA. Plate III, fig. 1, la. 
A. Testa turritd, anfractibus carinatis, et angulato-nodosis, nodis prominentibus 6 in ambitu. 
Anfractu ultimo gibbo, bicarinato; carind superiort prominentiori spinis acutis; in etate 
juniori digitis tribus parvis; in etate adultd digitis superioribus duobus longissimus. Cauda 
longd curvatd. Striis tenuissimis confertis transversis, plerumque obsoletis. 
Shell turrited, whorls carmated, angulated and carinated in their middle portion; 
nodules 6 in a volution. The last whorl has three carme, the last of which is nearly 
obsolete. In the young state it has three small digitations; when adult, the two superior 
carine are extended into very long digitations; the first carina having two angular pro- 
minences or spines. The entire surface of the shell has numerous fine encircling striz, 
which for the most part are indistinct. 
The acute spme, number of whorls, their prominently angular figure, together with the 
spine upon the middle of the superior carina of the last whorl, are characteristic features ; 
from 4. hamus and A. Phillipsii the character of the wing is sufficient to distinguish it. 
Locality. The planking beds of Minchmhampton Common have furmshed all our 
specimens ; the coarse character of the deposit rarely allows the display of the fine striae, 
or other features of much delicacy. It is moderately rare. 
Auaria HaMus, Des/. sp. Plate ITI, figs. 2, 2a, 26. 
RosTELLARIA Hamus, Deslongchamps. 1842. Mem. Soc. Linn. Normandie, vol. vii, 
p. 173, pl. 9, figs. 32, 33, 34, 35, 36. 
— — Desh. Lam. An. sans Vert., 2d Edit., 1843, tom. 9, p. 666. 
Prerocera HAMUS, D’Orb. 1850. Prod. Paléont, p. 270. 
A. Testa turritd, anfractibus transverse striatis, medio angulato-nodulosis, nodulis plus 
minusve crebris, ultimo anfractu gibbo, bicarinato, carind superiort majori ; apertura 
trigond. Carind majore ultimo anfractu nodulosa, nodulis parvis, subobsoletis. (Des- 
longchamps.) 
Shell turrited, whorls transversely striated, having a circle of nodules somewhat angu- 
lated in their middle part, the nodules bemg more or less closely arranged. The last whor! 
is large; it has two carine, the first of which is much the larger, and is indented or formed 
into closely arranged nodules, which are sometimes nearly obsolete. 
In some specimens, the larger carina is quite smooth, in others the indentations are 
oblique; the canal is short and straight. 
1 Mem. Soc. Linn. de Normandie, vii, p. 171, 176. Lam. Anim. sans Vert, 2d Edit., p. 671. 
