1824.] Mr. Dillwyn on Fossil Shells. 179 



strata, and still inhabits our land and waters. On the other 

 hand, all the carnivorous genera abound in the strata above the 

 chalk, but are comparatively extremely rare in the secondary 

 strata, and not a single shell has been detected in any older bed 

 than the lower oolite. As a proof of this rarity it may be 

 remarked, in the list of British fossils which Mr. Parkinson has 

 given in his Introduction to the Study of Organic Remains, that 

 not one single species of either of the carnivorous genera has 

 been referred to any stratum below the London clay, and only 

 the few following species appear in any of the numerous lists of 

 the secondary strata which are given in Conybeare and Phillips's 

 Outlines of Geology, viz. a Murex* and Pleurotoma rostrata in 

 the green sand, Ceritldum melanoides in chalk marie, and a few 

 species of Rostellaria in various strata from chalk marie to the 

 lower oolite. For the Pleurotoma and the Cerithium, a refer- 

 ence to the Mineral Conchology is given ; and Mr. Sowerby 

 there only says that he has seen an imperfect cast, very like the 

 former, from the canal at Devizes ; and of the latter, that it was 

 found in, the London clay, and in the clay above the chalk at 

 Newhaven. It is also worthy of remark, that all the above- 

 mentioned Rostellariae which have been found in secondary 

 strata are nearly allied to the Linncean Strornbus Pes Pelecani ; 

 and it may be observed that this species, when fully grown, has 

 not any open canal at its base ; and that in the figure which 

 Muller has given of the animal there is no appearance, nor in 

 Montagu's description is any mention made, of that retractile 

 proboscis or respiratory trunk, which are the distinguishing cha- 

 racters of a carnivorous Trachelipode. I therefore propose to 

 remove these Rostellariae of the secondary strata, which are 

 readily distinguished by the remarkable expansion of their outer 

 lips, to form a separate genus with Petiver's name of Aporrhais 

 and the other fossil Rostellariae which have the recent Strornbus 

 Jissus, for their type are only to be found in strata above the 

 chalk. 



Small circular holes, which have been bored by the predaceous 

 Trachelipodes, are frequently found in recent shells, and I have 

 seen exactly similar holes in many fossils, but they have all been 

 taken from the London clay or crag ; nor have 1 been able to 

 find any such appearance in any fossil of the older formations. 

 If this observation should be confirmed by a more extended 

 examination of other cabinets, it will prove that neither the 

 Aporrhaides, or any of those few undoubtedly carnivorous species 

 which have been found in the secondary formations, were fur- 

 nished with any such predaceous powers as Pliny has described, 

 and that they belong to a subdivision of the Trachelipoda zoo- 



" Mr. George Sowerby has sent uiethis shell with the name of Murrx calcar, anil if 

 I am not much mistaken, I have seen another species of Murex from the grccu band in 

 the extensive collection of Mr. J. S. Miller. 



N 2 



