ZOOLOGICAL AND BOTANICAL ASSOCIATION. 257 



sidered a bold innovator who had the temerity to separate the infra- 

 foraminated from the apically-foraminated species, and to rank the former 

 as a genus, now called Rhynchonella. But in what light are they 

 now considered ? The genus is regarded not only as the type of a family, 

 but even as the representative of an order (Helictobrachia), totally dis- 

 tinct from the one (Ancylobrachia) embracing the apically-foraminated 

 species or ordinary Terebratulidae. 



Leaving the present discussion, I may now state that I purpose in 

 this paper adhering to the view adopted in my " Monograph of the 

 Permian Fossils of England," which regards the Palliobranchs with re- 

 curved or subgyrated labial appendages as ordinally distinct from those, 

 in which these structures are spirally folded,* and as comprising a 

 number of families. In the work referred to I separated the species 

 containing a long loop from those having a short one under the name of 

 "Waldheimia ; but I did not, when doing so, sufficiently estimate other 

 differences which exist between them. For some time past, however, 

 the conviction has gradually forced itself on me, that these differences 

 are of sufficient importance to warrant a wider separation than a mere 

 generic one; and, in accordance with this view, I now propose to arrange 

 all the Ancylobrachs with a long loop, and some, which resemble them 

 in other particulars, under a new family, which may be termed Wald- 

 heimidae. By adopting this plan, not only do we properly estimate 

 certain structural characters which distinguish the species of the pro- 

 posed family from the short-looped Ancylobrachs or Terebratulidae, but 

 a practical answer is given to the first question alluded to in the begin- 

 ning. 



Many Palliobranchs possess, besides their brachial supports, two or 

 more plates attached to the hinge in one or both valves. In several 

 species the plates are separate, and stand more or less perpendicularly ; 

 but in others they are united by one of their edges, forming the various 

 shaped processes seen in Pentamerus, Camaraphoria, Merista, Lepta- 

 gonia, and other genera, as described by myself in 1846f and 1850. J 

 These plates and processes I have always considered to be muscular 



• Gray, the founder of this view, has designated these two orders respectively " An- 

 cylobrachia" and " Ilelictobrachia." 



t Vide " Remarks on certain Genera belonging to the class Palliobranchiata." 

 X Vide " Monograph of the Permian Fossils of England." 



