246 Dr Fleming on the British Testaceous Annelides. 
The characters of these three last shells remain to be determined. It is 
probable that they belong to the present genus, although Montagu seems 
inclined to consider them as free shells. The Serpula cornea of Adams, 
Linn. Trans, v. p. 5. tab. f. 33. 35. is no other than the Helix depressa 
of Montagu, a shell belonging to the Turbonidae *. 
II. — Extinct Species. 
10. S. amUguus — Shell of one whorl, finely wrinkled across, with a large 
central cavity, and a rounded mouth. Plate IX. Fig. 3. natural size and mag- 
nified. 
Ure, in his History of Rutherglen and Kilbride, is the first observer 
that has announced the occurrence of a fossil species of this genus, and 
in the coal formation. “ The Serpula planorhis may be ranked among 
the univalves. I have not met with more specimens than two or three, 
adhering to fragments of shells p. 309. Although there is no reason 
to believe that a recent shell ever occurred as a petrifaction, along with 
those which are extinct, in the independent coal formation, yet the evi- 
dence of Ure leads to the conclusion that he was acquainted with a fossil 
species, corresponding generally with the imperfect description which 
Linnaeus has given of his Serpula planorbis. This evidence is strength- 
ened by the circumstance, that I found the shell of which I have here 
given a representation, adhering to a Modiolus, from a thin bed asso- 
ciated with the limestone of the coal-field in the Cult Hills, and county 
of Fife. This species, which is probably the same with the one previous- 
ly observed by Ure, by belonging to the second section of the genus, is 
destitute of any obvious characters. 
* The true situation of this shell seems to be but imperfectly understood. 
It belongs to the genus Turbo of Linnaeus, (though inserted by Montagu 
along with serpuloides and unispiralis, to which it is closely related, in the ge- 
nus Helix), and to the Delphinula of Lamarck. It has been referred to, along 
Avith H. serpuloides of Montagu, by Captain Marryat, as an example of his 
genus Cyclostrema, (Linn. Trans, vol. xii. p. 338.) Doubts, however, may 
reasonably be entertained of the propriety of this alliance. All the British 
species noAv mentioned, as well as the Cyclostrema cancellata, being discoid 
shells, Avith an entire margin to the mouth, belong to Delphinula. A sub- 
division, however, of this genus, may be effected with advantage. If we 
restrict the genus Delphinula, so as to include only those species Avhich 
have a simple mouth, and whorls furnished with processes, as the recent 
Turbo delphinus of Linnaeus, and the fossil Delphinula calcar of Lamarck ; the 
genus Cyclostrema, having for its type C. cancellata of Marryat, will in- 
elude those species, having the Avhorls destitute of processes, but furnished 
with transA^erse ridges, the last formed one constituting a thickened margin to 
the mouth. Three species. Helix depressus, serpuloides, and unispiralis of 
Montagu, being thus excluded, call for the construction of a neAv genus, which 
Avill in some respects have the same relation to Cyclostrema, as Turritella 
bears to Scalaria. This genus I feel inclined to term Skenea^ in honour of 
Dr Skene mentioned above, whose labours, though but little known, justify 
this appropriation of his name. Several species of Skenea occur in a fossil state, 
among which may be noticed those figured by Mr Sowerby in his Min. Con. 
vol. i. plate 57. as Vermicularias : and it is probable that some of the species 
figured at plate 140. of the same work, as belonging to Planorbis, cequalis oxvA 
euomphalus^ should occupy a similar position. The species constituting Mr 
Sowerby’s genus Euomphalus, may be conveniently distributed among the 
three genera nnAA-^ established of an interesting astulideous family. 
