16 MOLLUSCA FROM THE GREAT OOLITE. 



to the first, and generally opposite to it, a character rarely if ever found in the recent 

 Pterocerae or Rostellariae. 1 



ALARIA ARMATA. Plate III, fig. 1, la. 



A. Testa turritd, anfractibns carinatis, et angulato-nodosis, nodis prominentibus 6 in ambitu. 

 Anfractu ultimo gibbo, bicarinato; carind superiori prominentiori spinis acutis ; in estate 

 juniori digitis tribus parvis ; in tstate adultd digitis superioribus duobus longissimus. Caudd 

 /mi //a curvatd. Striis tenuissimis confertis transversis, plerumque obsoletis. 



Shell turrited, whorls carinated, angulated and carinated in their middle portion; 

 nodules 6 in a volution. The last whorl has three carinae, the last of which is nearly 

 obsolete. In the young state it has three small digitations; when adult, the two superior 

 carinae 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 striae, 

 which for the most part are indistinct. 



The acute spine, 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 A. hamus and A. Phittipsii the character of the wing is sufficient to distinguish it. 



Locality. The planking beds of Minchinhampton Common have furnished all our 

 specimens ; the coarse character of the deposit rarely allows the display of the fine stria?, 

 or other features of much delicacy. It is moderately rare. 



ALARIA HAMUS, Desl. sp. Plate III, figs. 2, Za, 2t>. 



ROSTELLARIA HAMDS, Deslonffchamps. 1842. Mem. Soc. Linn. Normandie, vol. vii, 



p. 173, pi. 9, figs. 32, 33, 34, 35, 36. 



Desk. Lam. An. sans Vert., 2d Edit., 1843, torn. 9, p. 666. 

 PTEROCERA HAMUS, D'Orb. 1850. Prod. Paleont, p. 270. 



A. Testa turritd, anfractibus transverse strialis, media angulato-nodulosis, nodulis plus 

 minusve crebris, ultimo anfractu gibbo, bicarinato, carind superiori majori ; aperturd 

 Mffoiif!. 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 being more or less closely arranged. The last whorl 

 is large; it has two carinae, 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. 



