382 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. %% 



April 22, 1846. 



Captain Otter, R.N., and J. H. Perry, Esq., were elected Fellows 

 of the Society. 



The following communications were read v — 



1. On the Subdivision of the genus Terebratula. 

 By John Morris, Esq., F.G.S. 



The genus Terebratula is one of the most interesting of the family 

 Brachiopoda, inasmuch as it ranges under every variety of form 

 throughout the whole series of deposits from the palaeozoic to the 

 tertiary formations, and is found widely distributed, although not 

 numerous in species, at the existing epoch. 



The name Terehratulai first used by Llwyd, although not adopted 

 by Linnaeus, was appreciated by Bruguiere, and finally established 

 by Lamarck in the ' Systeme des Animaux sans Vertebres,' wliere 

 he classified and described a large number of species, which appear, 

 with additions, in the same work as re-edited by M. Deshayes. 



The great number of species which have been added of late years 

 to this genus has long made it desirable to subdivide it, and various 

 attempts have been made by different authors to establish subordi- 

 nate groups ; of these it is necessary to give some account before 

 proceeding to that which it is now proposed to substitute for them, 

 as being founded on the discovery of a different mode of classifi- 

 cation. 



Lamarck (1819) simply divided the Terebratulae into two groups, 

 namely 1. smooth, without longitudinal grooves, and 2. longitudi- 

 nally striated. Defrance (1827), in the ' Dictionnaire des Sciences 

 Naturelles,* followed this order in his notice of the fossil species, and 

 De Blainville did so also for the recent ones described in the same 

 work; the latter author however suggested another arrangement 

 founded on the greater or less development and form of the apophy- 

 sary system. 



Of the many special treatises on this genus, that by Baron Leo- 

 pold von Buch is the most important and perfect, as it attempts to 

 classify the various species upon sound principles and by a careful 

 examination of all the characters; and this classification indeed 

 forms to a certain extent the basis of the arrangement on which, 

 with some modifications hereafter proposed, the' Terebratulae may 

 be based. In this memoir* it will be perceived that Von Buch 

 classed the Terebratulae under three sections: 1st, " Umfassend" 

 the deltidial area completely embracing or surrounding the fora- 

 men ; 2nd, " Sectirend^' the deltidial area enclosing only a small 

 portion of the foramen ; and 3rd, " Discrete' the deltidial area not 



* Abhand. der Akad. der Wiss. zu Berlin, 1833, p. 36 ; Mem. de la Soc. Geol. 

 de France, torn. iii. p. 118. 



