202 On the Primary Divisions of the Brachiopods. 



and in the other ( Clistenterata) none. With these characters, 

 be it remarked, are generally coincident structural modifica- 

 tions of the hinge of the shell — the species with an anal aper- 

 ture having an inarticulating hinge generally, and those with- 

 out the anal aperture having a more or less interlocking one. 

 On one or other (or both) of these characters (and with coor- 

 dinate ones) these groups have been repeatedly recognized, 

 first by Owen, and then by Bronn, Huxley, and others. Owen, 

 it is true, vigorously opposed the assertion that any forms had 

 a ca?cal intestine ; but the groups he recognized were, as to 

 their constituents, exactly equivalent to the Tretenterates and 

 Clistenterates, although based only on the simple or interlock- 

 ing hinge and relative proportions of the viscera and brachia. 

 All other naturalists who have adopted the groups, however, 

 have especially recognized the perforation or non-perforation 

 of the intestinal tube in their diagnoses ; and the groups have 

 been adopted by the following naturalists, viz. : — 



Lyopomata, Owen, Encycl. Brit. 8th edit. vol. xv. p. 301, 1858 *. 

 Pleuropygia sen Ecar dines, Bronn, Klass. u. Ordn. Thierreichs, p. 301, 



1862f. 

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

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



vol. vii. p. 71, 1871. 

 Tretenterata, King, Aim. & Mag. N. H. (4) vol. xii. p. 15, 1873. 



II. 



Arthropomata, Owen, Encycl. Brit. 8th edit. vol. xv. p. 336, 1858 §. 

 Apygia seu Testicar dines, Bronn, Klass. u. Ord. Thierreichs, p. 301, 



1862 1| . 

 Artieulata, Huxley, Int. Class. An. p. 116,1869^1. 

 Arthropomata, Gill, Arr. Fam. Moll. p. 25, 1871 ; Dall, Am. Journ. 



Conch, vol. vii. p. 60, 1871. 

 Clistenterata, King, Ann. & Mag. N. H. (4) vol. xii. p. 15, 1873. 



' The conclusions of Prof. King (he being unaware of the 

 labours of his predecessors) are noteworthy, as being inde- 



* u Shell- valves inarticulated, and, save in the annectant family Cra- 

 niades, subcalcified ; viscera occupying one half, brachia the other half, of 

 the shell-cavity " (/. c. p. 339). 



t " Nahrungskanal (in den fossilen Sippen nur vermuthungsweise) 

 lang, gewunden, durch einen After (rechterseits ?) ausmiindend," &c. 

 (/. c. p. 301). 



X The intestine terminates in an anus on one side of the body " (I. c. 

 p. 116). 



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

 brachia two thirds, of the shell-cavity " (I. c. p. 336). 



|| " Nahrungskanal (bei den ganz fossilen Familien nur vermuthungs- 

 weise) mit einfachem abwarts gebogenem blind endigendem Darm- 

 Anhange (Afterlose)," &c. (I. c. p. 301). 



5f "The intestine ends in a blind sac " (/. c. p. 110). 



