38 



L.E. POPOV, L.R.M. COCKS AND I.F. NIKITIN 



Table 9 Measurements of ventral valves of Christiania aff. sulcata 

 Williams. Parastrophina-Kellerella Association, Anderkenyn-Akchoku 

 and Kujandysai sections. 





Lv 



W 



Iw 



Sw 



Lv/W 



Iw/W 



Sw/W 



N 



9 



9 



6 



5 



9 



6 



5 



X 



6.5 



5.6 



4.8 



2.5 



115.0% 



87.8% 



42.9% 



s 



1.91 



1.15 



0.85 



0.73 



16.1 



6.4 



12.4 



MIN 



4.0 



4.4 



3.9 



1.7 



90.9% 



82.8% 



23.0% 



MAX 



9.4 



7.4 



6.3 



3.2 



147.5% 



100.0% 



54.2% 



Lower Caradoc) of Girvan, Scotland, but differ in having an elongate 

 subtrapezoidal shell outline and two rounded plications flanking the 

 ventral sulcus. A characteristic feature of the Kazakh specimens is 

 the absence of high ridges bordering the dorsal adductor field 

 anteriorly, which also appear to be absent in C. sulcata (Williams 

 1962: pi. 18, fig. 36). Christiania aff. sulcata also differs from C. 

 egregia in having a stronger ventral median sulcus which is v-shaped 

 in cross-section, a distinctive dorsal median fold and significantly 

 smaller size. 



Family FOLIOMENIDAE Williams, 1965 

 Genus FOLIOMENA Havh'cek, 1952 



Type species. Strophomena folium Barrande, 1879, from the 

 Kralfiv Dvur Formation ( Ashgill) of Bohemia. 



Foliomena prisca sp. nov. PI. 3, figs 18-23, 25 



Etymology. After priscus, Latin - old. 



Holotype. BC 57405, PI. 3, figs 22, 23, a dorsal valve, from the 

 Anderken Formation, Sample 8255, Anderkenyn-Akchoku section. 



Material. 2 pairs of conjoined valves, 4 ventral and 3 dorsal 

 valves from Samples 100 (BC 57407), 2531, 8221 (BC 56890), 

 8223b, 8251, 8255 (BC 57402-06, 08), Anderkenyn-Akchoku sec- 

 tion; 628, 2538, 8217, Kujandysai section. 



Description. Shell flat and gently resupinate, transverse, 

 subrectangular in outline, about 60% as long as wide, with maximum 

 width at hinge line. Cardinal extremities near right angled. Anterior 

 commissure rectimarginate. Ventral valve gently convex in the pos- 

 terior half and weakly concave anteriorly. Ventral interarea apsacline 

 with a minute, apical pseudodeltidium. Dorsal valve with lateral 

 profile flat to slightly concave in the posterior half and convex 

 posteriorly, with maximum thickness at about three-quarters valve 

 length in mature specimens. Dorsal interarea linear, anacline. with 

 separate chilidial plates flanking narrow notothyrium. Radial orna- 

 ment of fine capillae rarely preserved. Concentric ornament of 

 numerous slightly uneven fine rugellae. 



Ventral interior with delicate teeth lacking dental plates and an 

 open, weakly impressed muscle field. Dorsal interior with a small 

 bilobed cardinal process in the low notothyrial platform and thin 

 widely diverging socket ridges. Thin median septum, about half the 

 length of the pair of strong curved side septa. 



Measurements. (463/12375) ventral valve, L=6.0, W=l 1.7; (464/ 

 12375) ventral valve, L=6.4, W=11.4; (466/12375) dorsal valve, 

 L=4.3,W=7.2; (468/1 2375) dorsal valve, L=4.6,W=8.5; (469/1 2375) 

 dorsal valve, L=3.6, W=6.3. 



Discussion. Cocks & Rong ( 1988:65) discussed the variation in 

 the ornament of Foliomena and noted that, although all the shells 

 from the type locality in Bohemia were devoid of radial ornament. 



occasional costae or costellae can be present sporadically in some 

 populations. The presence of fine capillae is a key feature in our new 

 species, as is the resupinate shell shape and the separate chilidial 

 plates, although the features within the interarea are poorly known in 

 Foliomena folium. It is difficult to make a precise comparison of our 

 shells with F. inelegans Fu, 1982 from the Pingliang Formation 

 ( Upper Caradoc) of North China, because of inadequate information 

 on the interior of the latter species. From F.jielingensis, described by 

 Zeng (1987) from the Miapo Formation (Lower Caradoc) of the 

 Yangtze Gorge area, south China, F. prisca differs in the presence of 

 the fine ornament, the resupinate shell shape and in the absence of the 

 ventral internal tuberculae seen in F.jielingensis. 



Superfamily PLECTAMBONITOIDEA Jones, 1928 



Family PLECTAMBONITIDAE Jones, 1928 



Subfamily TAPHRODONTINAE Cooper, 1956 



Genus ISOPHRAGMA Cooper, 1956 



TYPE SPECIES. Isophragma ricevillense Cooper, 1956. from the 

 Lower Caradoc of Tennessee, U.S.A. 



Isophragma imperator Popov, 1980 PI. 3, fig. 35 



1980 Isophragma imperator Popov: 147, pi. 2, figs 8-12. 



Holotype. CNIGR 25/1 1523, from Sample 1018. 7 km south-west 

 of Karpkuduk Well, Kotnak Mountains. 



Material. One pair of conjoined valves, 36 ventral and 34 dorsal 

 valves from Sample 1018. 



Discussion. Popov (1980) provided detailed description and dis- 

 cussion of this species. 



Family BIMURIIDAE Cooper, 1956 

 Genus CRASPEDELIA Cooper, 1956 



TYPE SPECIES. Craspedelia marginata Cooper, 1956: 773, pi. 2 13, 

 figs. 1-20, from the Pratt Ferry Formation (Landeilo), Alabama, 

 U.S.A. 



Craspedelia lata Popov, 1980 



PL 3, figs 26-34 



1 980 Craspedelia lata Popov: 55, pi. 1 7, figs 6-9. 



1986 Craspedelia tata Popov; Kolobova & Popov: pi. 1 , fig. 9. 



Holotype. CNIGR 8/ 1 1 098, from the Lidievka Formation (Lower 

 Caradoc), Belyi Kardon, north-central Kazakhstan. 



Material. 25 pairs of conjoined valves, 18 ventral and 5 dorsal 

 valves from Samples 100 (BC 56900-03, 57410, 57597) (=K98/ 

 1970), 626 (BC 56532, 56907-10, 57409, 57411-12), 8223a (BC 

 56935), 8223b, Anderkenyn-Akchoku section; Samples 8214 (BC 

 56925-30, 56932-33, 57598), 8215b (BC 56931), west side of 

 Ashchisu River; Samples 628 (BC 56911), 2538 (BC 56917-24), 

 Kujandysai section; Sample 8231^40, Buldukbai-Akchoku; Sample 

 948 (BC 56912-16), Tesik River. 



Description. Shell smooth, concavoconvex posteriorly, strongly 

 geniculated ventrally with a trail up to 8 mm long which curves back 

 postero-ventrally; semielliptical in outline, about 80% as long as 

 wide, with maximum width slightly anterior to hinge line. Cardinal 

 extremities rounded. Anterior commissure uniplicate. Ventral valve 

 strongly convex posteriorly with maximum thickness about one- 

 third anteriorly. Narrow and shallow sulcus anterior to the 



