REPORT ON THE BRACHIOPODA. 9 



never seen in either Terebratula or Terehratulina. There are, likewise, important differ- 

 ences between the two genera in the shape of the cardinal process and hinge-plate. The 

 characters of a genus must be taken from the full-grown animal and its shell, and not 

 from its immature condition, for, prior to its having attained its real and final character, 

 it has to pass through various and gradual changes. No one would describe a frog from 

 its young or larva, or when the tadpole presented a fish-like form, without feet or legs, 

 nor would the zoologist describe the animal or the loop of a fully-developed Waldheimia 

 from its early stages of development. Dr Jeffreys adopts Terehratella as a distinct 

 genus, while he considers Waldheimia as only a si\b-genus of Terebratula. In my 

 opinion the differences between Waldheimia and Terebratula are even greater than those 

 separating Terehratella from Waldheimia. 



In vol. iii. of the Geologist (p. 441, 1860), Mr Charles Moore made some observa- 

 tions On the Development of the Loop of Terehratella, having jjreviously submitted 

 for my inspection, opinion, and illustration, several examj)les of a small species he had 

 discovered in the Oolites of Hampton Cliff, near Bath. I made the enlarged drawings 

 which were subsequently badly reproduced in pi. xiii. of that periodical. Mr Moore's 

 observations and my illustrations proved that a certain modification of the loop takes 

 place prior to its having attained its final and full-grown condition. In a subsequent 

 paper by Mr C. J. A. Meyer, entitled On the Development of the Loop and Septum in 

 Terehratella (Geol. Mag., vol. v. p. 268, 1868), the author dissents from the views 

 exjDressed by Mr C. Moore, and adds : " With regard, therefore, to the attachment or non- 

 attachment of the loop at different ages of the shell in the sections Waldheimia, Tere- 

 hratella, Sec, the rule appears to be that the loops are either constantly attached to the 

 septum, as in Terehratella, Megerlia, &c., or constantly free, as in Waldheimia ;" but 

 this is a mistaken view. Dr S. P. Woodward and I observed in 1853, that a 

 modification in the development of the loop of the sub-genus Terehratulina took place 

 from the young to the adult, for we showed that when quite young, and up to a certain 

 age, the loop was very short and simple as in Terehratida, but that with age it was 

 rendered annular by the gradual union of the oral processes. The subject was, however, 

 in 1875, seriously taken into consideration by Herman Friele,' when he pointed out that 

 the skeleton of Waldheimia cranium, Moll., and Waldheimia septigera, Loven, under- 

 went a peculiar change, that the apophysary system exhibited a much more complicated 

 construction at an early stage of growth, than at that of maturity. In a subsecjuent 

 paper, illustrated by six well-drawn plates, H. Friele continues his investigations on this 

 important question,^ and states : " Having resumed the study of Waldheimia, I have 

 become satisfied that my description given of the young state of the apophysary system 



' Bidrag til Vestlandets Mollusk fauna, Cliristiania, Videnskabs-Selskabets Forhandlinger. 



^ The Development of the Skeleton in the Genus Waldheimia, Archiv for Mathematik og Natun'idenskab. 

 Christiania, 1877. 



(ZOOL. CHALL. EXP. PART I. — 1880.) A 2 



