32 Mr. J. Morris on some new species of the genus Ancyloceras. 



eleven species having been described tberefrom, four of which 

 belong to the inferior and seven to the superior stage of this 

 formation, all of them being specifically distinct from those 

 of the British Isles. In England this gemis also commences 

 with the inferior oolite, from which two species have been 

 obtained ; it is again found in the Kelloway rock, but attains the 

 full numerical development, as in France, in the lower part of 

 the cretaceous series, and does not reappear in any of the supe- 

 rior deposits. In the ' Catalogue of British Fossils,' the genus 

 Cj'ioceras is mentioned as occurring in the Kelloway rock of 

 Wilts ; not having, however, at that period any specimens for 

 examination, and having recently entertained some doubts on this 

 point, in consequence of Mons. D'Orbigny stating that this 

 genus is peculiar to the cretaceous system*, I have re-examined the 

 whole subject, and by the inspection of a fine series of specimens 

 kindly placed at my disposal by ]\Irs. Lowe, ]\Ir. Channing Pearce 

 and Mr. S. P. Pratt, it would appear, that the specimens generally 

 found in collections from the Kelloway rock, under the name of 

 Crioceras, are only the spiral volutions or chambered portion of 

 Ancyloceras, the produced or hooked parts containing the last 

 chamber being mostly wanting. There appears to be some diffi- 

 culty in distinguishing the genera Ancyloceras and Crioceras 

 when the chambered portion of the former is only preserved, 

 both of them agreeing in having the spiral volutions distinctly 

 separated from each other, and the lobes of the septa being 

 formed of " parties impairesf/' whilst in the genus Scaphites, 

 to which Ancyloceras is closely allied, the lobes are formed of 

 " parties pairesj." 



Ancyloceras Callovicnsis. (PI. VI. tig. 3. a — d.) 

 A. testa oblonga, transversim sequaliter costata, costis acutis, latera- 



liter tuberculatis ; dorsobi tuberculato ; anfractibus compressius- 



culis; apertura ovali. 



Spire composed of tln-ee rather compressed volutions, f. 3 b, 

 each volution having about twenty-eight elevated ribs, slightly 

 inflected posteriorly, and partially interrupted between the dorsal 

 tubercles; in well-preserved specimens there are traces of inter- 

 mediate smaller ribs. The ribs ornamented with two conical 

 tubercles on the dorsal part (f. 3 d), and one nearly centrally 

 placed on the internal portion of each side. The last volution 

 produced into a straightish line (f. 3 a), which is recm'ved at 

 the extremity when in a perfect state. 



Mouth oval or somewhat hexagonal. The foliations of the 



* " Les Crioceras ne paraissent avoir vecu qu'k la jieriode cretacde — infe- 

 rieiire. lis se soiit seuieinent montres, ju&qu'a present, dans le terrain neo. 

 comien et dans le gault." — Terr. Cretaces, p. 458. 



t Terr. Cret., pp. 45?, 492. J Ibid p. 513. 



