ordovician brachiopoda 121 



Table 92 



Statistics of length (1) and length (tl) of pedicle tubes in n pedicle valves of Bicuspina subquadrata 

 sp. nov (A) and Bicuspina modesta sp. nov. (B) 





A 



B 



n 



1 mm (var 1) 



tl mm (var tl) 



r 



IO 



u-39 (11-677) 

 1-41 (o-668) 

 0-865 



24 

 7-54 (3-423) 

 0-85 (0-215) 



o-434 



logel (var logel) 



2-3897 (0-0862) 



1-9907 (0-0584) 



logetl (var logetl) 

 a (var a) 



0-1988 (0-2896) 



0-887 



1-8330 (0-10570) 



0-2927 (0-2603) 

 o-457 



2-III2 (0-16440) 



Table 93 



Statistics of length (1) and lateral extension of sockets (br) in n brachial valves of Bicuspina 

 subquadrata sp. nov. (A) and Bicuspina modesta sp. nov. (B) 



A B 



n 7 17 



1 mm (var 1) 10-21(10-858) 7-46(8-487) 



br mm (var br) 3-37 (0-930) 1-95 (0-596) 



r 0-887 0-905 



a (var a) 0-2927 (0-00365) 0-2650 (0-00084) 



CAEROPLECIA gen. nov. 



Name. A triplesiid with a concentric ornament like the end threads (Gk. KaZpos) 

 in a loom. 



Diagnosis. Subcircular, dorsibiconvex, uniplicate triplesiids with a strongly 

 convex brachial valve and a gently convex to flat pedicle valve, bearing respectively 

 a flat-topped fold and complementary sulcus arising anterior of the umbo ; ventral 

 interarea short, apsacline, pseudodeltidium narrowly folded medially, foramen 

 supra-apical, dorsal interarea linear ; radial ornamentation of coarse costae and 

 branching costellae originating during later stages of shell growth, concentric 

 ornamentation of delicate rounded ridges (fila). 



Ventral interior with variably developed pedicle tube, small teeth supported by 

 short acutely divergent dental plates, muscle scars broadly bilobed with low median 

 ridge dividing narrow adductor band ; mantle canal pattern unknown. 



Dorsal interior with short forked cardinal process, divergent rod-like brachio- 

 phores, and small oblique sockets ; fine median ridge dividing quadripartite adductor 

 scars with anterior pair larger than posterior ; mantle canal pattern unknown. 



Type species. Caeroplecia plicata sp. nov. from the Whittery Shales, Shropshire. 



Discussion. The new genus is unique among triplesiaceans in being concentri- 

 cally ornamented by fine, rounded ridges instead of overlapping lamellae. The 

 delayed development of radial ornamentation, the subcircular outline and the flatfish 

 pedicle valve together also distinguish Caeroplecia from all other triplesiid genera. 



