APPENDIX. 319 



RISSOA THERMALIS? LinncBus. Tab. XXXI, fig. 12, a, b. 



TURBO THERMALIS. Linn. Syst. Nat., 12th ed., p. 1237, No. 629. 

 MURIATICUS? Beudant. Ann. du Mus., torn, xv, p. 201. 



Spec. Char. " T. umbilicatd oblongiusculd, obtusd, anfractibus teretibus Icevibus." Linnseus. 



Shell elongately conical or subulate, naked, smooth, and glossy ; volutions six, slightly convex ; 

 suture distinct and deep ; apex obtuse, depressed ; aperture ovate ; inner lip adpressed, giving a pointed 

 termination at the upper part; umbilicus small. 



Length, ^ inch. Diameter, f of the length. 



Locality. Clacton. 



It is now most difficult, perhaps impossible, to say what Linnseus intended for the type of his Turbo 

 Thermalis, as there are two or three species that might, with a moderate allowance of latitude in variation, 

 be made to accord with the diagnosis of his shell, and, it is to be feared, have already been done so. I am 

 unwilling to make " confusion worse confounded," so have introduced our shell with the above name 

 instead of imposing a new one, though not without great misgivings upon the propriety of doing so, 

 particularly as Linnaeus, in his description, says, " T. semine Brassicse paulo major." 



Our fossil is by no means rare at Clacton, but the majority of my specimens were obtained from the 

 clay or estuary portion of the deposit at that locality in association with marine or rather estuary species : 

 Cardium edule, Tellina Balthica, Trigonella plana, Mytilus edulis, and Balanus. I have also found 

 specimens in the sandy and purely fresh-water part of the cliff, with land and fresh-water shells, so that 

 probably its animal inhabitant was capable of residing in water that was either fresh or brackish. Mr. 

 John Pickering has presented me with some specimens of a recent shell identical with our fossil, and these, 

 he tells me, were obtained in the ditches of brackish water near Gravesend, in Kent. Similar specimens 

 were pronounced by Messrs. Forbes and Hanley, vol. iv, p. 267, to be only varieties of R. ventrosa, in which 

 opinion I cannot coincide ; and I am permitted by Mr. Pickering to say he believes the two shells to be 

 specifically distinct. 



This shell, or something very like it, was found by MM. Ehreuberg and Von Hemprich, " in fontibus 

 Oasis Jovis Hammonis inter Alexandriam et Rosettam." 



JEFFREYSIA? PATULA, S. Wood. Tab. XXXI, fig. 14, a, b. 



NATICA DEPRESSULA. S. Wood. Catal. of Crag Shells, Ann. and Mag. Nat. Hist., 1840, 



p. 530. 



Spec. Char. Testd minuld, subglobosd, Icevigatd, politd, tenui, vitred, pellucidd? umbilicatd; apice 

 obtuso ; anfractibus paucis 1 2 depressis ; suturis profundis, excavatis ; aperturd magnd, ovatd, dilatatd ; 

 labro simplici acuto. 



Shell small, subglobose, smooth, glossy, thin, vitreous, pellucid? umbilicated; apex obtuse; volutions 

 few, 1 2, depressed ; suture deeply excavated ; aperture large, ovate, expanded ; outer lip thin and 

 sharp. 



Diameter, ^ inch. 



Locality. Cor. Crag, Sutton. 



Three specimens of a small species were found by myself many years since, and reserved to the present 

 time. They are now assigned provisionally to the above genus, more from the difficulty of finding a better 

 position than from a satisfaction of their correct appropriation. They appear to differ from Natica, where 



