ORDOVICIAN BRACHIOPODA 93 



the Aldress sample, in the inherently greater width of the brachial valve. The 

 Llandeilo species also differs from the Meadowtown and Aldress stocks in the shape 

 parameters and relative growth of the cardinalia. 



In contrast to these decisive specific differences, the relationship between the three 

 Shelve samples is much more complicated. The Meadowtown sample, herein 

 recognized as the new species D. salopiensis, differs from both the Spy Wood and 

 Aldress stocks in the more acutely divergent attitude of the dental plates ; and 

 additionally from the former in the residual length of the ventral muscle scar 

 and the divergence of the brachiophore bases. It differs from the latter in the 

 relative width of the brachial valve. Moreover there is also a significant difference 

 (p < o-ooi) in the residual shape of the brachial valve of the Aldress and Spy Wood 

 samples. These relationships are most conveniently expressed by assuming that 

 the Aldress and Spy Wood samples constitute two new subspecies, D. salopiensis 

 transversa and D. salopiensis gregaria respectively. 



The stratigraphic ranges of these taxa are well defined. The small number of 

 moulds collected from the Betton Beds are indistinguishable from D. salopiensis. 

 A larger sample of specimens from the Rorrington Beds, on the other hand, differs 

 from D. salopiensis at least in the degree of divergence of the dental plates (p < o-ooi), 

 but they proved to be identical in every respect with the new Spy Wood subspecies 

 D. salopiensis gregaria. 



Neither D. salopiensis (s.l.) nor D. parva are like other Anglo- Welsh Dalmanella. 

 D. indica (Whittington) appears to be most closely related, but comparisons of 

 statistical data for that species (Williams 1963 : 382-385) with those for D. parva 

 and D. salopiensis (s.l.) reveals significant differences in a number of features in- 

 cluding the parallel disposition of the brachiophore bases in the older species and 

 especially in the simplicity of their ribbing patterns which are essentially : ia, 1, 

 2a, 2, 3a, 3b, 3, 4al, 4a, 4, 4a . 



Table 55 



Statistics of length (1) and maximum width (w) of n brachial valves of Dalmanella parva Williams 

 (A), D. salopiensis sp. nov. (B), D. salopiensis gregaria sp. et subsp. nov. (C) and D. salopiensis 



transversa sp. et subsp. nov. (D) 





A 



B 



C 



D 



n 



42 



82 



46 



14 



1 mm 



2-76 



2-06 



2-28 



2-62 



(var 1) 



(o-54) 



(0-461) 



(o-443} 



(0-814) 



w mm 



3-57 



2-73 



3-o9 



3-59 



(var w) 



(o795) 



(0-522) 



(o-55) 



(1-148) 



r 



0986 



0-972 



o-955 



o-993 



logel 



0-9808 



0-6721 



0-7845 



0-9078 



(var logel) 



(0-0685) 



(0-1029) 



(0-0815) 



(0-1119) 



log e W 



1-2429 



0-9708 



1 -099 



1-2364 



(var log e w) 



(0-0603) 



(0-0675) 



(0-0561) 



(0-0851) 



r e 



0-989 



0-976 



o-959 



o-993 



a 



0-9384 



o-8i 



0-8294 



0-8723 



(var a) 



(0-00049) 



(0-00038) 



(0-00126) 



(0-00088 



