3. REVISION OF THE FAMILIES OF LOOP- 

 BEARING BRACHIOPODA* 



(Plates XIV and XXIV) 



The recent publications of Fischer and CEhlert,^' ^- 1"- f 

 combined with previous observations by Friele ^^ and Des- 

 longchampsj furnish material which suggests a natural 

 grouping of the terebratuloids. The present knowledge is 

 incomplete in some details, especially as regards the fossil 

 genera, yet enough is available to simplify the arrangement 

 of the leading terebratuloid types, and to show their common 

 relationships. By far the best classifications have been those 

 proposed by Dall ^ in 1870, and by Deslongchamps ' in 1884. 

 Only in the light of recent discoveries is it possible to offer a 

 new arrangement of the genera. 



The sub-order Ancylobrachia, proposed by Gray ^^ in 1848, 

 includes, with some emendations, all the genera currently 

 known as terebratuloids. Taking Gray's name for the entire 

 group, since it has priority over Kampylopegmata, Waagen,^^ 

 1883, it is found to comprise two distinct types of brachial 

 structure, each with a separate genetic history. It is here 

 proposed to recognize these two types as of family impor- 

 tance, according to the interpretation of family characters 

 given by Agassiz.^ 



The TerehratulidcB. 



In the first family, the Terebratulidse, the loop is always 

 free and may be long or short. It is developed by the growth 



* Trans. Conn. Acad. Set., IX, 376-391, 395-398, pis. i, ii, 1893. 



t The works referred to by numbers are cited in full in the list appended. 

 An excellent summary and review of Fischer and ffihlert's papers, s, 9, lo \,y Migg 

 Agues Crane,2 appeared in the Jannary number of Natural Science, 1893. 



