BRITISH AVONIAN CONODONT FAUNAS 149 
Magnilaterella sp. 
Plate 23, fig. 9 
MATERIAL. I specimen: figured, X 244. 
RANGE. Scotland GILM z. 
DEscrIPTION. A single specimen of doubtful affinities is referred to this genus. 
It is characterized by the distinctive callus developed on the inner face of the lateral 
bar and the slit-like excavation developed on both bars. The posterior bar is very 
short and may not be broken. The lateral bar bears two denticles which are discrete, 
inclined and sharply pointed ; the bar is broken and is of unknown length. The 
posterior bar bears a single denticle at its junction with the lateral bar ; the denticle 
is short but sharply pointed, being only about one sixth to one seventh the length of 
the posterior bar. 
Magnilaterella spp. 
Plate 23, fig. 10 ; Plate 31, figs. 5, 11 
MATERIAL. 649 specimens : figured, X 242, X 322, X 323. 
RANGE. Avon Gorge Z 35-C 24, North Crop CYD 6-3D 17. 
DESCRIPTION. Fragmentary specimens of Magnilaterella are relatively common 
in the upper part of the D Zone and elsewhere. Few of them are sufficiently com- 
plete to enable specific identification, but some of them probably represent new 
species. We illustrate three extreme forms. 
Plate 31, fig. 11 (X 322) shows a form with characteristically deep and strong 
posterior bar, the inner lateral face of which bears a well-developed callus and basal 
groove, which is thin but conspicuous and long. The apical denticle is very strongly 
developed, and has four to five times the basal width of other denticles of the posterior 
bar. The lateral bar is very strongly flexed, and the denticles decrease rapidly in 
size towards the distal end. 
Plate 31, fig. 5 (X 323) shows a form characterized by much more slender construc- 
tion. The apical denticle is elongated and gently curved posteriorly and inwards. 
It is sharply pointed and its general construction is slender. The callus is con- 
spicuous, but shallow, and the lateral bar, which lies at about go0° in both a horizontal 
and vertical plane to that of the posterior bar, has its main flexure at its junction with 
the posterior bar rather than being continuously recurved. 
Magnilaterella ? sp. 
Plate 23, figs. 7a, b 
MATERIAL. I specimen : figured, X 447. 
Rance. North Crop ZLA 37. 
DESCRIPTION. This specimen consists of an antero-lateral and a posterior bar. 
The major denticle is smaller than the denticles on the posterior bar and lies in 
