ordovician brachiopoda 59 



Table 39 



Statistics of length (1) and maximum width (w) of 9 brachial valves of Nicolella cf. actoniae 



(Sowerby) 



1 mm (var 1) 7-93 (12-915) 



w mm (var w) 12-37 (26-845) 



r 0-978 



a (var a) I '44 I 7 (0-0128) 



Table 40 



Statistics of length (1) and maximum depth (th) of 15 pedicle valves of Nicolella cf. actoniae 



(Sowerby) 



1mm (var 1) 11-53 (12-595) 



th mm (var th) 3-66 (1-41) 



r 0-854 



a (var a) 0-3346 (0-00234) 



Table 41 



Statistics of length of pedicle valve (1) and length of ventral muscle scar (sc) for 12 specimens of 



Nicolella cf. actoniae (Sowerby) 



1 mm (var 1) 12-79 (3-019) 



s"c mm (var sc) 4-29 (0-481) 



r 0-802 



a (var a) 0-3991 (0-00568) 



Table 42 



Statistics of length of pedicle valve (1) and anterior extension of dental plates (dl) of 7 specimens 



of Nicolella cf . actoniae (Sowerby) 



1 mm (var 1) H'73 (6-778) 



dl mm (var dl) 1-91 (0-332) 



r 0964 



a (var a) 0-2212 (0-0007) 



valve the Whittery sample is intermediate between N. actoniae and the significantly 

 deeper Bala subspecies and, when allowance is made for the variability of the 

 samples, comparable with both in the inherent profile and rate of deepening of the 

 pedicle valve. 



The development of the ribbing does, however, indicate the much closer affinity 

 with N. actoniae than with the Welsh subspecies. In the number and wavelength 

 of costae the Whittery sample is like both N. actoniae and its subspecies. However, 

 in all 8 brachial valves between 8-5 and 14-2 mm long, no costellae arise within 

 7-5 mm of the umbo and only 3 out of 8 valves show any branching, which consists 

 solely of the appearance of 3a in two specimens and 4a arising before 3a in the third. 

 The Whittery sample is therefore more like N. actoniae in the rare development of 

 costellae within the size range stipulated above, and also in being less thick-shelled 

 than the Bala subspecies at such stages in growth (Williams 1963 : 356). 



