THE BRITISH FOSSIL BRACHIOPODA. 349 



that it is only in a very few recent genera and species that this investigation can be 

 carried out, and that we can never know anything relating to the conditions of the intes- 

 tine in the very large number of genera now extinct. 



. In an interesting paper by Theodore Gill " On the Primary Divisions of the Brachio- 

 poda ,n it is stated that " these two groups have been repeatedly recognised, first by 

 Prof. Owen, and then by Bronn, Huxley, and others." Owen, it is true, vigorously 

 opposed the assertion that any forms had a caecal intestine, but the groups he recognised 

 were, as to their constituents, exactly equivalent to the Tretenterata and Clistenterata, 

 although based only on the simple or the interlocking hinge and the relative proportions 

 of the viscera and brachia. All other naturalists who have adopted the groups, however, 

 have especially recognised the perforate or non-perforate condition of the intestinal tube 

 in their diagnosis. Two groups have been thus adopted by the several naturalists, as 

 follows : 



I. 

 Lyopomata, Owen, 'Encycl. Brit.,' 8th ed., vol. xv, p. 301, 1858. 



" Shell valves inarticulated, and, save in the annectant family Craniada, sub- 

 calcified ; viscera occupying one half, brachia the other half, of the shell- 

 cavity " (I.e., p. 339). 

 Pleuropyyea, seu Ecardines, Bronn, ' Klass. u. Ordn-Thierreichs,' p. 301, 1862. 

 " Nahrungskanal (in den fossilen Sippen nur vermuthungsweise) lang, gewunden, 

 durch einen After (rechterseits ?) ausmundend," &c. (I.e., p. 301). 

 Inarticulata, Huxley, 'Int. Class. An.,' p. 116, 1869. 



"The intestine terminates in an anus on one side of the body ' (1. c, p. 116). 

 Lyopomata, Gill, ' Arr. Fam. Moll.,' p. 26, 1871. Dall, 'Am. Journ. Conch,' vol. 



vii, p. 71, 1871. 

 Tretenterata, King, 'Ann. and Mag. Nat. Hist.' (4), vol. xii, p. 15, 1873. 



II. 



Arthropomata, Owen, 'Encycl. Brit.' 8th ed., vol. xv, p. 336, 1858. 



" Shell-valves articulated, calcareous ; viscera occupying one third, brachia two 

 thirds of the shell-cavity (1. c, p. 336). 

 Apygea, seu Testicar dines, Bronn, 'Klass. u. Ord. Thierreichs,' p. 301, 1S62. 



" Nahrungskanal (bei den ganz fossilien Familien nur vermuthungsweise) mit 

 einfachem abwarts gebogenem blind endigendem Darm-Anhange (After- 

 lose), &c." (1. c, p. 301)." 

 species of Brachiopoda, and which may be seen in the Museum at Ottawa. A series of very interesting Brazilian 

 Carboniferous species have been described by Prof. Derby, and is now in the museum at Kio de Janeiro. 



Klipstein's valuable collection of the St. Cassian Brachiopoda has been purchased by the British 

 Museum. 



1 'Annals and Mag. of Nat. Hist.,' 4th ser., vol. xii, p. 202, September, 1873. 



