80 BRITISH AVONIAN CONODONT FAUNAS 
REMARKS. In some specimens there is a slight asymmetry of the posterior 
platform, the inner lateral posterior margin tending to be more strongly outflexed 
than the outer. The platform is widest on its oral edge and, especially in its posterior 
half, tapers rapidly towards its aboral margin. 
Cavusgnathus convexus Rexroad 
Plate 14, figs. 2a—d 
1957 Cavusgnathus convexa Rexroad : 17, Pl. 1, figs. 3-6. 
1958 Cavusgnathus convexa Rexroad ; Rexroad: 16, Pl. 1, figs. 12-14. 
1961 Cavusgnathus convexa Rexroad ; Rexroad & Collinson: PI. 1. 
1964 Cavusgnathus conveva Rexroad ; Rexroad & Furnish : 670, Pl. 111, fig. 1. 
1965 Cavusgnathus convexa Rexroad ; Rexroad & Nicoll: 17, Pl. 1, figs. 14, 15. 
MATERIAL. 5 Specimens : figured, X 63. 
RANGE. Avon Gorge S 20-S 41, North Crop 3D 13. 
DEscRIPTION. The margins of the inner and outer parapet are straight. A deep 
trough runs the length of the platform and occasionally a few nodes form a carina at 
its posterior extremity. The parapets are ornamented by regularly spaced, trans- 
verse ridges. In lateral view, the anterior blade is seen to consist of six laterally 
compressed denticles, which are fused nearly to their apices. The anterior blade is 
highest near, but not at, its posterior extremity and this gives the blade a convex 
oral edge. The anterior blade, which is less than one third the total length of the 
unit, is free for half its length. The oral edge is convex and the aboral edge is 
straight to slightly arched. The posterior edge is rounded. The basal cavity is of 
moderate depth and asymmetrical ; it is long, extending for two thirds the length of 
the unit, and reaches the posterior extremity of the unit. The inner is more flared 
than the outer. A keel runs from the anterior edge of the basal cavity to the 
anterior extremity of the unit. 
Cavusgnathus cristatus Branson & Mehl 
Plate 14, figs. 3a—d 
1940 Cavusgnathus cristata Branson & Mehl: 177, Pl. 5, figs. 26-31. 
1947 Cavusgnathus cristata Branson & Mehl; Cooper (partim) : 91, Pl. 20, figs. 4-6 ; 
(non Pl. 20, figs. 7—10). 
1953 Cavusgnathus cristata Branson & Mehl; Hass: 77, Pl. 14, figs. 12-14. 
1956 Cavusgnathus cristata Branson & Mehl; Elias: 115, Pl. 11, figs. 1-6. 
1956 Cavusgnathus cristata var. grandis Elias : 115, Pl. 11, figs. 12-14. 
non 1957 Cavusgnathus cristata Branson & Mehl; Bischoff: 19, Pl. 2, figs. 7a, b. (=C. 
naviculus.) 
1958 Cavusgnathus cristata Branson & Mehl ; Rexroad : 16, Pl. 1, figs. 15-17. 
1961 Cavusgnathus cristata Branson & Mehl ; Rexroad & Burton : 1151, Pl. 138, fig.16. 
1961 Cavusgnathus cristata Branson & Mehl ; Rexroad & Collinson: PI. 1. 
MATERIAL. 8 specimens : figured, X 64. 
RANGE. Avon Gorge D 26, North Crop 3D 14/15-3D 22. 
