100 DEVONIAN FOSSILS 
to determine the nature of the external ornament, which is impor- 
tant in this case. For this reason the fossil is referred with some 
reserve to Quadrifarius, but it has the long ventral median septum 
and dental plates found in that subgenus (Fuchs 1923, Asselbergh 
1930, 1931, Dahmer 1942). The long median septum and dental 
plates are seen also in smaller ventral steinkerns on specimens 
27,216 (from G 23) and 27,232 (from G 25). 
Genus PROTOLEPTOSTROPHIA Caster, 1939 
Protoleptostrophia affinalata sp. nov. 
Pl. IT, Fig. 6; Pl. III, Figs. 19, 22. 
Type Material. Holotype consisting of the steinkern of a ven- 
tral valve, specimen 27,214. There are more than twenty shells of 
this species on the slab or rock containing the holotype, along with 
a dorsal valve of Chonetes baragwanatht. The holotype is marked 
with an “А” on the specimen. Paratype consisting of a steinkern 
of a dorsal valve on the same slab of rock as the holotype. The 
paratype is marked with a “В” on the specimen. 
Description of Holotype. Ventral valve slightly convex, sub- 
semicircular. Width as preserved 2-7 cm., probably З em. when 
complete; length 2 cm. Shell has a few weakly-developed, discon- 
tinuous, concentric wrinkles. Hingeline greatest width of shell; 
cardinal angles alate. Interarea makes an angle of the order of 
120° (measured with the eye only) with the plane of the shell. 
Teeth file occupies only about one-quarter of the height of the 
area, which is about 1 mm. Teeth vertical (i.e., at right angles 
to the hingeline), fine, and even, there being approximately 3 
per mm. 
Muscle field well defined by dental ridges which form an angle 
of about 40° (though in other specimens it ranges as high as 707); 
about 12 mm. long, i.e., more than half the length of the shell. At 
the posterior end, the muscle field is very narrow, then spreads out 
anteriorly. At the fine posterior apices of the diductor scars, on 
each side of the median septum, there are pronounced knobs on 
the steinkern which represent cavities on the original shell. The 
muscle scars are striate, and on each side of the median septum 
the diductors are divided by ridges into three more or less equal 
areas. The median septum is broad and low. At the posterior end 
the septum is characterized by a superimposed median furrow 
(ridge in steinkern) about 3 mm. long. 
Outside the muscle field, the whole inner surface of the shell is 
very finely and closely papillose, the papillae extending right to 
