﻿'^8 ME. S. S. EUCKMAN 0^ BRACHIOPOD [Feb. 1 908, 



Spirifer lata ^ : he cites as synonym ' Phillips, S^:). glabra, pi. x, 

 fig. 12.' At any rate, these forms with dental plates are not 

 Sp. glabra ; they belong to Reticidaria, and may be referred to, at 

 present, as R. lata (I J. 



In his pi. xi, figs. 3 & 4, Davidson depicts a thin, very transverse 

 shell; and he remarks (p. 62) that de Koninck suggests the name 

 Sp. glaberrimus for this form. It is well to adopt this suggestion, 

 taking fig. 3 as the tj^pe. Of this thin, transverse form there are 

 specimens in the British Museum ([^Tatural History) from Kildare. 

 Of these, B 20857, a rather large example, shows strong dental 

 plates ; B 20859, a small specimen, has a broken beak, exposing 

 the dental plates in section ; in B 20858 the presence of the plates 

 is not certain, on account of test, but there is a suggestion of 

 reticulation. In another specimen, the largest registered under 

 ' Spirifer glaber, I^o. 43400,' the dental plates are well shown. 



On this evidence Sp. glaberrimus must be removed from the 

 ^Za6e>--series, and must be classed as a Reticularia : it is closely allied 

 to H. elliptica (Phill.) ; its likeness in shape to that species suggested 

 that it was a Reticularia before the fact of the dental plates was noted. 



In other forms ranged under Sp. glabra quite a different ancestry 

 is evident. Davidson depicts (pi. xii, figs. 3-5) forms with faint 

 radial ribbing. The likeness of Sp. linguifera, Phillips (Davidson, 

 pi. xii, fig. 4) to Sp). ovalis (Dav. pi. ix, fig. 20) forces the suggestion 

 that the former is the smooth development of the latter. 



On similar grounds of likeness in shape it seems possible to 

 suggest that >S).7. glabra (Dav. pi. xi, fig. 1) is the much- accelerated 

 smooth form of Sp). eximius, de Koninck (Dav. pi. x, fig. 12), and 

 that Sp. oblatus (Dav. pi. xi, fig. 8) is the smooth form of 

 Sp. pingiiis (Dav. pi. x, fig. 6). Then >S'p. glabra (Dav. pi. xii, 

 fig. 3) looks as if it were the j'^oung form of pi. xi, fig. 2, well 

 enough preserved to show faint radial ribbing : in that case, 

 the form in pi. xi, fig. 2, looks like a smooth development of 

 ^ Sp. subrotundatus ' (Dav. pi. x, fig. 10). 



The type of Sp. decora, PhilL, shows traces of faint radial 

 costation ; but it is not easy to suggest the costate ancestor in this 

 case : Sp. planata (Dav. pi. vii, figs. 25-36) and Sp. Reedii (Dav. 

 pi. V, figs. 40-48) look something like what one would expect such 

 a form to be. 



If the various costate forms, Sp. pinguis, Sp). ovalis, etc., are kept 

 under distinct names as distinct species, it follows that if the smooth 

 forms be their derivatives, those smooth forms must be kept under 

 distinct names : they cannot be grouped together as Sp). glaber. 

 Further, the forms derived from reticulate ancestors must be 

 separated not only specifically but generically from those derived 

 from radially-costate ancestors. 



Thus the British forms called Spirifer glaber are a very hetero- 

 geneous series. It may be doubted whether foreign species so 



^ ' Illustr. Fo;>s. Concb.' 1844, p. 112 & pi. li, fig. 24. 



