39G GENERAL SUMMARY TO 



From these Tables it will be seen how very much more numerous, both generically 

 and specifically, were the Brachiopoda in our British rocks during the Palaeozoic period, 

 and likewise how few species we appear to have discovered that pass with certainty from 

 one geological period into another. Many of the species seem also to be restricted to 

 certain zones of the same formation, but I am firmly convinced that when better under- 

 stood a larger number will be found that have passed the limits, often no doubt, 

 arbitrarily assigned to them by palaeontologists, who generally like, if they can do so, to 

 see species restricted to one formation, even one horizon or zone. Of late years it has, 

 however, become apparent, through the valuable researches of Sig. Seguenza and 

 others, that a number of Upper-Tertiary or Pliocene species still live on our sea-bottom. 

 In an announcement made by M. Paul Fischer in the ' Bulletin of the Geological Society 

 of France' for March, 1884, that distinguished French malacological observer, while 

 alluding to a large Pliocene Dentalium that had been recently dredged alive at 440 

 metres in the Atlantic, as well as a species of Cadulus, says, " Les faits qui se multiplient 

 depuis quelque temps permettent de supposer qu'un grand nombre de formes reputees 

 fossiles vivent encore dans les grands fonds de la mer, et que, par consequent, les 

 differences entre la faune Pliocene et la faune actuelle sont beaucoup moins sensibles 

 qu'entre la faune Miocene et la faune Pliocene." Thus Terebratulina caput-serpentis is 

 well known to occur in the Pliocene of Sicily and in the Crag of England ; and, indeed, 

 some Cretaceous specimens of T. striata bear so near a resemblance to some Mediter- 

 ranean variations in form of T. caput-serpentis that they are scarcely distinguishable, and 

 several so-termed Recent and Tertiary forms of the genus may have been derived from 

 the Cretaceous type, and are possibly no more than varieties of it. Again, the large 

 recent Japanese T Crossi, Dav., much resembles some specimens of the Cretaceous 

 Terebratulina De/rancii, although we may not be able to assert that they are identical. 



Terebratula vitrea and its var ? minor occur in the Pliocene rocks of Sicily, and are 

 still alive in the surrounding sea-bottoms. We know how near it also resembles some 

 specimens of Ter. carnea from the Upper Chalk. 



Waldheimia septigera, Loven, is not a rare species on northern sea-bottoms. It 

 occurs also in the Pliocene rocks of Sicily. It had received from Prof. Seguenza the 

 name of W. peloritana, but in a paper entitled " Sull antica distribuzione geographica 

 di talune specie malacologiche viventi," 1 Seguenza admits that his W. peloritana and 

 Loven's W. septigera are one and the same species. The Terebratula septata of 

 Philippi is a Terebratella, and is both generically and specifically distinct from Loven's 

 type — Waldheimia Baphaelis, Dall, from Japanese waters, seem to be nearly related to 

 Waldheimia septigera. 



Waldheimia cranium, Muller, occurs both recent and fossil. It is found fossil in the 

 Pliocene rocks of Sicily. 



1 ' Unlletino Malacologico Italiano,' auno iii, 1870. 



