THE BRITISH FOSSIL BRACHIOPODA. 299 



seriously taken into consideration by Herman Friele, 1 when he pointed out that the 

 skeleton of Waldheimia cranium, Miiller, and Wold, septigera, Loven, underwent a pecu- 

 liar change, the apophysary system exhibiting a much more complicated construction 

 at an early stage of growth than at maturity. In a subsequent paper, illustrated by six 

 well drawn plates, Herr Friele continued his investigations on this important subject, 2 

 and stated : " Having resumed the study of Waldheimia, I have become satisfied that 

 my description given of the young state of the apophysary system and its development 

 was, in the main, correct, i.e. the apophysis of Waldheimia is at an early stage fastened in 

 a threefold manner; firstly, the lamella? are connected to the hinge-plate by the crura; 

 secondly, the lamellae are connected with the septum ; and, finally, the reflected part of 

 the loop is connected with the lamellae and the septum by two vertical walls placed close 

 together. As the shell is enlarged the loop expands in breadth, the united lamellae split 

 from below upward, dissolve connection with the septum, and the lateral walls vanish. 

 In this representation no correction is to be made ; but, besides being now enabled to 

 proceed one step further in the development, I can also replace my earlier simple 

 drawings by better and more complete illustrations." Herr Friele then proceeds to 

 describe in detail each modification assumed by the loop, from its complicated condition 

 up to its simple adult form, in which it is attached only by its crura to the hinge-plate. 

 He adds : " The history of the development of the Brachiopoda has until recently been 

 very little known, and it was not till 1871 and 1873 that Professor Morse published 

 a complete description of that of Terebratulina septentrionalis? By comparing the 

 manner in which the formation of the apophysary system takes place in the latter, with 

 the above described in Waldheimia, an essentia] difference is observed ; Terebratulina 

 proceeds without deviation direct towards the form that characterises the genus ; Wald- 

 heimia, on the contrary, forms first a very complicated loop and passes then to one of a 

 more simple construction." 



In the ' Proceedings of the Zoological Society ' for 1878, Dr. Gwyn Jeffreys corrobo- 

 rated the observations of Herr Friele; and I likewise noticed, in "Challenger" 

 material, that a similar development in the loop as that observed in Wald. cranium and 

 Wald. septigera takes place in Wald. Kerguelensis and Wald.flavescens, and that this is 

 probably the rule in every species of the genus. A similar modification of the loop 

 occurs in Wald. lenticularis, a species nearly related to Wald. Kerguelensis. 



These important questions and investigations relative to the development of the loop 

 in different genera and species are, as it were, a new study, which, when properly 

 followed up, will eventually lead to the most important results. It will now, therefore, 



1 ' Bidrag til Vestlandets Mollusk-Fauna, Christiania, Videnskabs-selskabets Forhandlinger ' for 18/5, 

 p. 57. 



2 " The Development of the Skeleton of the genus Waldheimia," ' Archiv for Mathematic og Natur- 

 videnskab,' Christiania, 1880. 



3 " Early stages of Terebratulina septentrionalis" ' Mem. of the Boston Soc. of Nat. Hist.,' vol. ii, 

 parts 1 and 3. 



40 



