BRITISH AVONIAN CONODONT FAUNAS 179 
occurs 150 ft. below the first appearance of S. aculeatus, but in another it occurs 
with S. aculeatus and Palmatolepis glabra. Sandberg & Klapper (1967) have also 
found the genus Clydagnathus in several sections in Wyoming and Montana, and the 
genus Patrognathus in the Windy Gap Formation of Wyoming, where it is associated 
with S. sulcatus (see also p. 54) 
The Lower Devonian Eognathodus Philip differs from Patrognathus in the form of 
the anterior blade, although the genera resemble one another in overall form. 
Patrognathus variabilis gen. et sp. nov. 
Plate 2, figs. 8a—11c 
DERIVATION OF NAME. From the great variability of this form. 
Diacnosis. Elongate, symmetrical form, possessing lanceolate platform and 
medial blade. Carina absent. Posterior denticle of blade twice as large as other 
blade denticles. Cavity flared, elongate, covering most of platform. Base of 
cavity and blade grooved. 
MATERIAL. 625 specimens: Holotype X 311, Paratypes X 519, X 309, X 310 
(all figured). 
TYPE LOCALITY AND HORIZON. Avon Gorge, K Zone. Sample KLz. 
RANGE. Avon Gorge Samples K 1-K 17, North Crop Samples KL 1-KL 12. 
DEscRIPTION. The unit is symmetrical, the platform being lanceolate and 
straight to slightly curved. The blade varies in length, but is commonly a little 
A. Oral view B. Aboral view 
High denticle of blade 
Platform High denticle of blade 
Anterior Posterior 
__— Anterior edge 
“~ Platform denticle 
~* Flared basal cavity 
Position of basal cavity 
_- High denticle of blade 
; Oral edge 
Anterior edge —_ vad 3 
eh 
Posterior edge 
\ ~Aboral edge 
Position of basal cavity 
C. Lateral view 
Fic. 34. Patrognathus sp. showing morphological terms used in the text. 
