APPENDIX. 



Besides the few Supplementary additions which this Appendix may ontrin, it is desirable to point 

 out several corrections resulting from the continued researches undertaken during the four consecutive 

 years devoted to the publication of the present Monographs. Nor was it always possible to avoid certain 

 changes and repetitions resulting from the mode in which the material had unavoidably to be assembled. 



INTRODUCTION. 



Page 5, line 13. 



For " the recent Atrypa 1 and the fossil Rhynchonellidee, which latter, from the general analogy of the 

 structure of their shell, might be supposed to have the respiratory organs at the same low degree of 

 development as the Terebratulidce, and to have the same need," read "the Rhynchonellidse, which have the 

 respiratory organs at the same low degree of development as the Terebratulidce have the same need" (Owen). 



Page 7, line 3. 

 For "perforated valve, d," read "imperforated valve, d" (Owen). 



Page 9, line 1 . 

 For "called 'thecidium,' " read "called ' deltidium' " (Owen). 



Page 33, line 23. 

 Place T.lunifera (Philippi) under the genus Morrisia (line 22). 



Page 44. 



Add — Mr. S. P. Woodward places the Rudistes in his seventh Family of Conchifera, and states that — 

 " They are the most problematic of all fossils ; there are no recent shells which can be supposed to belong 

 to the same family ; and the condition in which they usually occur, has involved them in greater obscurity. 

 (1. Buch regarded them as Corals. 2. Desmoulins, as a combination of the Tunicary and Sessile 

 Cirripede. 3. Dr. Carpenter, as a group intermediate between the Conchifera and Cirripeda. 4. Prof. 

 Steenstrup, of Copenhagen, as Anellides. 5. Mr. Sharpe refers Hippurites to the Balani ; Caprinella 

 to the Chamacese. 6. Lapeirouse considered the Hippurites, Orthocerata ; the Radiolites, Ostracea* 

 7. Goldfuss and D'Orbigny place them both with the Brachiopoda. 8. Lamarck and Rang, between the 

 Brachiopoda and Ostracece. 9. Cuvier and Owen, with the Lamellibranchiate bivalves. 10. Deshayes, in 

 the same group with JEtheria. 11. Quenstedt, between the Chamacece and Cardiacece.) The characters 

 which determine their position amongst the ordinary bivalves, are the following : — 1. The shell is composed 

 of two distinct layers. 2. They are essentially unsymmetrical, and right-and-left valved. 3. The 

 sculpturing of the valves is dissimilar. 4. There is evidence of a large internal ligament. 5. The hinge- 

 teeth are developed from the free valve. G. The muscular impressions are two only. 7. There is a 



1 The shell referred to as a "recent Atrypa," is the Rhynchonella psittacea (Int. pi. vii, fig. 100 — 102). 

 It does not belong to the genus Atrypa which is furnished with shelly spires (see pi. vii, fig. 89 and 92). 



1 



