138 GASTEROPODA OF THE INFERIOR OOLITE. 



superficial resemblance. It is a didactyl Alaria, which probably belongs to the 

 tr if da-group (Hamicaudcs). It differs from Alaria Lorieri in the excessive 

 sharpness and salience of tbe keels, and in the numerous spinous processes on the 

 keels of the spire- whorls ; it further differs in the extreme recurvation of the 

 posterior digitation, reminding one somewhat of the curve in the tusk of the 

 mammoth. 



Occurs in the Parkinsoni-zone (P x ) of Vitney Cross with Alaria Lorieri and 

 Spinigera recnrva. 



With this species the list of didactyl Alarice comes to an end. Some other 

 Aporrhaids remain to be described, which it will be convenient to classify under 

 Section 3, as belonging to no group in particular, or whose position is somewhat 

 doubtful. 



Section 3. 

 57. Alaria spinigera, Lycett, 1853. Plate VII, fig. 4. 



1853. Eostellaeia sptnigeka, Lycett . Proc. Cotteswold Nat. Field Club, vol. i, 



p. 80. 



Description by Author. — "Spire elevated, acute; whorls few, each with seven 

 prominent spines or spinous ribs; body-whorl spined above, grooved beneath, 

 wing not digitated and but moderately expanded ; caudal extremity straight and 

 moderately long." 



The specimen (fig. 4) forms part of the Lycett collection in the Jermyn Street 

 Museum, but, as Lycett gives no figure, strictly speaking there can be no type- 

 specimen. The specimen now figured is marked " B. spinigera, Nailsworth," 

 apparently in Lycett' s handwriting. 



The length is 15 mm. and the spiral angle about 45°. The shell is sub- 

 elongate, thick, and rugose, body-whorl and spire about the same height, apex 

 somewhat acute. There is one prominent and highly-spinous keel on the body- 

 whorl, which gives rise to a sharp, stumpy, upcurved digitation after the manner 

 of the Monodactyls (hence, if we may judge from this specimen, it is not quite 

 correct to say that the wing is not digitated). 



The aperture is wide-triangular to trapezoidal, and forms a sort of angle 

 posteriorly in connection with the short process which represents the digitation. 

 The columella is very straight, and probably the canal also. There is an indica- 

 tion in the figured specimen of an anterior digitation. This would relegate the 



