Vol. 62.] BRACHIOPOD HOHCEOMORPHY. 455 



Discussion. 



The Chairman (Mr. A. Strahan) regretted the absence of the 

 Author and the cause to which it was due. The thanks of the 

 meeting were due to Dr. Bather for the lucid exposition which he 

 had presented iu the short time available. 



Dr. F. A. Bather noticed that the Author had not attempted to 

 explain the origin of the peculiar lobation of the diphyoid Tere- 

 bratulae. Presumably it was connected with the desirability of 

 affording more room for the respiratory arms. The tendency was 

 constantly observable in Brachiopods, from Orthis biloba down to the 

 present day ; but whether the exaggerations of it were due to a 

 decrease in the oxygen of the water could not be decided. It was 

 interesting to compare the perforation with the lunules in certain 

 sea-urchins of the family Scutellidse, where, owiug to the flatness 

 of the test, room was provided for the inter-radial internal organs 

 by projections of the test, which ultimately met, leaving radial 

 perforations. But the main interest of the comparison, in view of 

 the Author's conclusions, was that this development had arisen 

 independently in at least three genera — Encope, Mellita, and 

 Rotala. 



In reply to a question asked by Dr. Marr, the speaker explained 

 that, although the general succession shown in the Author's diagram 

 appeared to be well founded, still the precise horizons of many 

 forms described by the older writers had not yet been definitely 

 settled. 



