BRITISH AVONIAN CONODONT FAUNAS 223 
anterior migration of the lateral denticle in stratigraphically younger specimens in 
the present faunules, but the samples are too small to justify any firm conclusion. 
Spathognathodus bischoffi sp. nov. 
Plate 4, figs. Ia—4c 
1956 Spathognathodus costatus (E. R. Branson) Bischoff & Ziegler : 166, Pl. 13, fig. 3. 
1957 Spathognathodus costatus (E. R. Branson) Bischoff : 56, Pl. 4, fig. 28. 
1957 Spathognathodus costatus (E. R. Branson) Ziegler in Fliigel & Ziegler ; Pl. 1, figs. 15, 18 
only. 
1959 Spathognathodus costatus (E. R. Branson) Helms: Pl. 111, figs. 2-4. 
1959 Spathognathodus costatus (E. R. Branson) Voges : 297, text-fig. 5, fig. 1. 
1962 Spathognathodus costatus costatus (E. R. Branson) Ziegler : 107, 108, Pl. 14, figs. 1-6, 
8-10. 
DERIVATION OF NAME. In honour of Dr. G. Bischoff. 
Diacnosis. Elongate spathognathodid with, a greatly laterally expanded 
pseudopolygnathid-type basal cavity, a central oral blade of very uniform, confluent, 
blunted denticles, and a series of about twelve strong, low, regular, laterally-elongate 
nodes developed along whole inner length of unit except for anterior blade. Outer 
oral surface of cup may be feebly nodose. 
MATERIAL. 10specimens : Holotype X 4o1, Paratypes (all figured) X 398, X 400, 
X 399. 
TYPE LOCALITY AND HORIZON. Honnetal, West Germany to VI Zone—Upper 
costatus Zone, Roadside cutting (Ziegler 1962). 
DESCRIPTION. These elongate spathognathodids have an anterior blade two to 
three times as deep as the posterior end of unit. The anterior blade consists of about 
3 to 4 confluent, but apically discrete denticles, their apices being bluntly pointed. 
The anterior edge is straight and deep, making an angle of 80°—go° with the aboral 
Anterior denticie 
Loteral denticles A 
* 4 
Oral edge 
_—- Anterior edge 
VERT LE 
; LIES _—Antero-aboral angie 
Posterior edge —— <a 
/ \ 
/ eas 
/ / \ anterior portion of 
fe / blade 
/ 
Posterior portion of blad 
hal ab Aboral edge 
Basal cavity 
Cavity lips 
Fic. 46. Spathognathodus sp. showing morphological terms used in the text. 
