46 



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



Tesikella necopina (Popov, 1980) 



PI. 5, figs 30, 31, PI. 6, figs 1-6 



1980 Palaeostrophomena necopina Popov: 145, pi. 1, figs 8-1 1 . 



HOLOTYPE. CNIGR 15/1 1523 (L=l 1.4, W=16.8), dorsal internal 

 mould, Anderken Formation, east side of Kopalysai, Sample 127/K- 

 1970. 



Material. Five pairs of conjoined valves, 60 ventral and 43 dorsal 

 valves from Samples 8128, 8129 (BC 57432-34, 57604), 8138, 

 Anderkenyn-Akchoku section; Sample 7613, Kujandysai section; 

 Sample 127/K-1970 and Rukavishnikova (1956) Sample 34 (BC 

 56881), east side of Kopalysai; Sample 818a (BC 57435), Burultas 

 Valley; Sample 1024b, east side of Karatal near Sorbulak well; 

 Samples 1018, 1018a, area 7 km south-west of Karpkuduk well, 

 Kotnak Mountains. 



DESCRIPTION. Shell profile resupinate, transversely subrectangular 

 outline, about 55-60% as long as wide with maximum width at the 

 hinge line. Cardinal extremities slightly acute to near right angled. 

 Anterior commissure rectimarginate, broadly rounded. Ventral valve 

 with lateral profile slightly convex in the umbonal area, gently 

 concave anteriorly. Ventral interarea low, planar, catacline with a 

 well developed, narrow pseudodeltidium. Dorsal valve with moder- 

 ately convex lateral profile, flattened posteriorly with low anacline 

 interarea and separate chilidial plates. Radial ornament parvicostellate 

 with 10-12 parvicostellae per mm in mature specimens and accentu- 

 ated costellae of two-three generations. 



Ventral interior with strong, double teeth lacking dental plates and 

 large divided musle field with strong diductor scars and muscle 

 bounding ridges extending anteriorly to the mid-valve. Adductor 

 scars small, strip-like, divided by a fine median ridge, about half the 

 length of the diductor scars. Subperipheral rim variably developed, 

 posterior to which is a weak median ridge. Mantle canals saccate 

 with very short vascula media branching just beneath the anterior 

 margin of the diductor scars. Dorsal interior with trifid cardinal 

 process on a low notothyrial platform and low, widely diverging 

 socket ridges. Median septum strong and narrow, about 75% as long 

 as the valve and joined anteriorly to a low subperipheral rim. 

 Adductor scars radially arranged with smaller anterior pair extend- 

 ing anteriorly to mid-valve. 



Discussion. Popov (1980) originally attributed the species to 

 Palaeostrophomena, but since then the internal characteristics, par- 

 ticularly of the ventral valve, have become known, and it is clear that 

 this species cannot properly be attributed to that genus. 



DISCUSSION. These specimens closely resemble Sortanella 

 quinquecostata Nikitin & Popov (1996: 9) in radial ornament, 

 posteriorly subcarinate ventral valve and gently uniplicate anterior 

 commissure. The type locality is about 400 km to the north-west of 

 our localities, and occurs in the overlying Dulankara Regional Stage 

 which is late Caradoc rather than early to middle Caradoc. Because 

 no dorsal interiors are known, the species cannot yet be identified 

 from the Anderken Formation with certainty. 



Subfamily AEGIROMENINAE Havh'ek, 1961 

 Genus CHONETOIDEA Jones, 1928 



Chonetoidea sp. 



PI. 5, figs 4, 5 



Type SPECIES. Plectambonites papillosa Reed, 1905, from the 

 Slade and Redhill Mudstone Formation (Middle Ashgill), 

 Pembrokeshire, Wales. 



Material. One internal and one external mould of a pair of 

 conjoined valves, BC 56537 (L=3.2, W=5.1) from Sample 8255, 

 Anderkenyn-Akchoku section. 



Description. Shell planoconvex, transverse, semielliptical in out- 

 line with maximum width at the hinge line. Cardinal extremities 

 acute. Anterior commissure rectimarginate. Ventral valve gently 

 convex in lateral profile with maximum thickness slightly anterior to 

 the apex. Interarea low, planar, anacline with minute apical 

 pseudodeltidium. Dorsal valve flat with a low, anacline interarea. 

 Chilidial plates separate. Radial ornament finely and unequally 

 parvicostellate with five accentuated primary ribs and four second- 

 ary costellae originating at about mid valve length. 



Ventral interior with small, bilobate muscle field bisected 

 posteriorly by low median ridge. Dorsal interior with simple under- 

 cut cardinal process joined to minute socket ridges subparallel to the 

 hinge line. Median ridge originating anterior to the deep alveolus and 

 extending to mid- valve. Six septulae lateral to the anterior part of the 

 median ridge near the mid-valve. 



DISCUSSION. These specimens resemble Chonetoidea virginica 

 Cooper ( 1956: 805 ), from the Edinburg Formation of Virginia, in the 

 size and outline of the planoconvex shell, unequally parvicostellate 

 radial ornament, and number and arrangement of septulae in the 

 dorsal valve. 



Family HESPERONOMIIDAE Cooper, 1956 

 Genus ANOPTAMBON1TES Williams, 1962 



Family XENAMBONITIDAE Cooper, 1956 



Subfamily XENAMBONITINAE Cooper, 1956 



Genus SORTANELLA Nikitin & Popov, 1996 



TYPE SPECIES. Sortanella quinquecostata Nikitin & Popov, 1 996, 

 from the Dulankara Regional Stage (Upper Caradoc), north Betpak- 

 Dala, Kazakhstan. 



Sortanella aff. quinquecostata Nikitin & Popov, 1996 



PI. 6, figs 26-33 



Material. Ten pairs of conjoined valves, 7 ventral and 8 dorsal 

 valves from Samples 100 (=K98/1970) (BC 57459), 626 (BC 57000, 

 57006-9, 57458), Anderkenyn-Akchoku section; Samples 628, 2538 

 (BC 5677 1,568 10, 570 10-03, 57460, 88), Kujandysai section; Tesik 

 River, Sample 948 (BC 57002-5). 



TYPE SPECIES. Leptaena grayae Davidson, 1883, from the 

 Craighead Limestone (Upper Caradoc) of Girvan, Scotland. 



Anoptambonites convexus sp. nov. 



PI. 7, figs 5-26; Figs 12.1-12.6 



1986 Anoptambonites sp.; Kolobova & Popov, pi. 1, figs 7. 8. 



ETYMOLOGY. After convexus, Latin - convex. 



HOLOTYPE. BC 57462, PI. 7, figs 5, 6, a dorsal interior from 

 Sample 100, Akchoku Mountain. 



Material. 36 pairs of conjoined valves, 21 ventral and 14 dorsal 

 valves from Samples 1 00 (=K98/1 970) (BC 56540, 570 1 4-32, 57462, 

 64, 69, 71), 626 (BC 57466, 68), 8214 (BC 57480), 8223 (BC 

 57063-68), 8223b (BC 57467), Anderkenyn-Akchoku section; Sam- 

 ples 628 (BC 56530, 42, 57043-51). 2538 (BC 56531, 57052-61, 



