24 MOLLUSCA FROM THE GREAT OOLTTE. 



Locality. It would appear to be very rare, and has been found only in the planking of 

 Minchinhampton Common ; but with this and other minute shells it is not easy to form an 

 accurate notion of their actual numbers. In the Bath Oolite of Langrune, Normandy. 

 (Desl.) 



Brachytrema. Nov. Gen. 

 Fusus. Species in part. Auct. 



The Great Oolite shells, which we have placed under this generic designation, present 

 characters so much at variance with the received ideas of Fusus, that we have been induced 

 to erect them into a new genus, under the name Brachytrema ; the definition of this form, 

 whether it be regarded as subdivision of Fusus, or as a distinct genus, is as follows : — 



B. Testa turritci, turbinatd ; anfractibus convexis et costatis, nodulosis, aut cancellatis; 

 labro dextro lenui ; columella rotundald, lavi, ad basin contortd; canali brevi, obliquo. 



Shell small, turreted, turbinated ; whorls either costated, nodulated, or cancellated ; 

 the last whorl large and ventricose; right lip thin and smooth ; columella smooth, rounded, 

 twisted near to the base, and reflecting outwards, forming a short oblique canal ; aperture 

 moderately large, subovate, its length being usually less than that of the spire. 



The general figure of this genus is turbinated, and nearer to Buccinum than Fusus ; it 

 has, however, the base and channel of Cerithium ; the short oblique canal and twisted 

 columella separate it from Fusus, the genus to which the known species have most 

 frequently been referred. The following forms may possibly be assigned to this genus : — 

 Murex haccanensis of Phillips, the Fusus carinatus of Roemer, the Triton buccinoideum, the 

 Purpura Jilosa, the Murex versicostalus, and the Fusus corallensis of Buvignier, and, pro- 

 bably, the Fusus nassoides and the Fusus nodulosus of Deslongchamps. All the species are 

 small, the largest scarcely equalling 10 lines in length. 



The Fusus Thorenti d'Archiac would appear at first sight to belong to this genus; but 

 having examined the original specimens in the collection of Viscomte d'Archiac, we are 

 inclined to believe that the figure in the 'Memoirs of the Geological Society of France' 

 (vol. v, plate 30, fig. 8), is taken from an imperfect shell, which is closely allied to, if not 

 identical with, the Turbo pyramidalis of the same author. 



Brachytrema buvignieri. Plate V, fig. 7. 



B. Testa conicd, turbinatd, apice obtuso; anfractibus 5 planatis, et costulatis; costis (14) 

 longitudinalibus, elatis, lineas transversa^ numerosas, elatas, distantes yerentibus. 



Shell conical, turbinated, apex obtuse, whorls 5, flattened and costated; costae longi- 

 tudinal, elevated, about 14 in a volution, and impressed by transverse lines : the lines are 



