146 BRITISH AVONIAN CONODONT FAUNAS 
denticle of the lateral bar, being about equal in height to the larger denticles of the 
posterior bar. 
When viewed aborally the most striking feature of this species is the broad 
extension of the aboral surface, represented by the flange, and the restriction of the 
warped and flexed sinuous cavity to the outer lateral margin of the scar, which the 
flange forms. 
Magnilaterella clarkei sp. nov. 
Plate 23, figs. 11-13b 
1900 Polygnathus convexus Hinde (partim) : 342, Pl. 9, fig. 7. 
1928 Lonchodus convexus (Hinde) Holmes (partim) : 14, Pl. 6, fig. 14. 
1960 “Gen. et sp. nov?’”’ Clarke : 16, Pl. 11, figs. 10, 12, 13. 
DERIVATION OF NAME. After Dr. W. J. Clarke. 
Diacnosis. Magnilaterella characterized by massive development of strongly 
depressed, continuously curved posterior bar, gently flexed inward in its median part, 
its denticles tending to be largest in its mid-third. Denticles of lateral bar large, 
sub-triangular, separated by smaller single denticles. Posterior bar of insignificant 
size in comparison with lateral bar, but strongly inflexed. 
MATERIAL. 23 specimens: Holotype X 431, Paratypes X 241, X 432 (all 
figured). 
RANGE. Scotland DUN 52-80, GILM 3-BIL 1ro2. 
DeEscrIPTION. This is a rather typical species of the genus Magnilaterella, with a 
very elongated and very deep posterior bar, which becomes deeper in its posterior 
part. It has a very feebly convex inner-lateral face and is bowed slightly out- 
wards along itslength. It is continually recurved with a conspicuous concave aboral 
surface. The oral surface bears up to 4 main denticles, which tend to be largest in 
the median third and decrease in size in both directions. They are conspicuously 
triangular in lateral view and are sharply pointed. The denticles have very sharp 
Inner lateral face 
LS) 
“ye Lateral bar 
Posterior 
bar 
Basal groove 
Fic. 29. Magnilaterella sp. showing morphological terms used in the text. 
