LIOCERAS CONCAVUM. 61 



suture-line agrees very fairly therewith ; but its ribs seem much too straight on 

 the lateral area. (This may be an error in drawing ; the curvature of ribs is a 

 feature which has received neither the notice which it deserves, nor the atten- 

 tion sufficient to ensure perfect accuracy.) The specimen is said to have 

 come from the Upper Lias, and it has evidently nothing to do with the genus 

 Lioceras. 



Dumortier ('Etudes Paleont.,' vol. iv, pi. 13, figs. 1 to 3) depicts a shell, from 

 the zone of Am. bifrons, which is very much nearer to our species, and belongs to 

 the same genus. It possesses the same suture-line and concave inner margin, and 

 fig. 1 has a very similar umbilicus ; but it differs in having very fine striations, 

 instead of the ribs characteristic of Lioc. concavum. 1 Prof. Blake 2 quotes 

 Harpoceras concavum (Sowerby), from the zone of Am. annulatus at Whitby; 

 but this must be an incorrect identification, for, from the synonyms which he gives, 

 he is evidently referring to Lioc. elegans (Young). 



The typical Lioceras concavum is not so common as some of its varieties. It 

 occurs in the Concavnm-beds of Bradford Abbas and near Halfway House, 

 Dorset. With its varieties it forms the leading, and by far the most 

 abundant, shell in what has been called " the Cephalopoda-bed of Bradford 

 Abbas ;" and it characterises the same horizon in a somewhat similar lithological 

 bed at Halfway House and in neighbouring quarries. Some forms have also been 

 obtained from near Sherborne, Dorset, and from Stoford, Bast Coker, and 

 Corton Denham in Somerset : Sowerby's type came from near Ilminster in that 

 county. All these places are situated either in North Dorset or South Somerset, 

 and generally not far from the border-line which divides the two counties. I 

 cannot remember to have collected it from any of the exposures in South Dorset, 

 namely, near Broad Windsor, 3 Bridport, &c. From Dundry Hill, in North 

 Somerset, I possess two specimens. This hill, which I have lately had an oppor- 

 tunity of visiting, is usually considered to be an outlier of the Cotteswolds ; 

 but pakeontologically, and especially geologically, it strikingly recalls the Dorset 

 strata, while it has little resemblance to those of the Cotteswolds. I was not 

 fortunate enough to obtain any specimen of Lioc. concavum there, nor to detect its 

 horizon; but several examples from this locality are preserved in the Bristol 

 Museum, showing, like the Dorset specimens, considerable variation. From the 

 Cotteswold Hills themselves, or from the Inferior Oolite of any other part of 

 England, I have neither collected a specimen nor found one among those sent by 



1 See p. 39. 2 ' Yorkshire Lias,' p. 303, 1876. 



3 This is not now correct. By recent work, done while this sheet was passing through the press, 

 I have discovered many specimens of this species at Horn Park and Stoke Knap, near Beaminster. 

 Both places are about one mile from Broad Windsor. At the former the Concavum-bed is not a foot 

 thick ; at the latter it is four feet thick, if not more ; while it is absent at Coney gore just the other side 

 of Broad Windsor. 



