114 



ROCHESTER ACADEMY OF SCIENCE. 



[March 14, 



ignorance as to the true relationship between the calcified loop of the 

 Terebratulidre and spiral processes of the Helicopegraata. 



In the Report on the Salt Range Fossils of India, (Mem. Geol. 

 Surv., India, Series XIII, Productive lime-stone fossils, IV, fasc. 3., 

 pp. 549-550, Calcutta, 1884), Waagen proposed the following arrange- 

 ment of the Hinged-Brachiopoda ( Arthropomata) as an expression of 

 his idea of the affinities of the various families : 



Atrypidee. 



Camerophorinre. 



Athyrida^. 

 I 



Nucleospiridre. 



SpiriferidK. 



J 



Pentamerinre. Rhvnchonellidoe. Terebratulidre. 



Enteletes, 



Porambonitidai. 



I 



Leptocoelia. 



I 

 (Tropdoleptus.) Productidae. 



I J 



Strophomenidffi. 



J 



Orthis. 



In this classification it will be seen that ^Vaagen makes the Athy- 

 rid?e and Spiriferidte, through the Nucleospiridai to be the successors or 

 descendants of the TerebratulidcX. 



Davidson, commenting upon a letter from Waagen, communi- 

 cating the above classification, (Mon. Brit. Foss. Brachiopoda, Vol. V. 

 pp. 389-390) remarked : 



'•The subject will, however, demand much further consideration, 

 for the passage between the loop-bearing Terebratulids and the 

 spiral-bearing Spiriferidre has not yet been discovered." This remark 

 of Davidson was published in the last month of 1884, and I have been 

 unable to find that any one since then has been able to throw light 

 upon the difficulty involved. 



The following suggestions will, I think, point to the nature of the 

 modifications by which these two important groups of Brachiopods 

 were differentiated. 



In attempting to explain the relationship of the several families 

 of Brachiopods in a course of lectures on the History of Organisms, 

 (delivered at Cornell University, this particular lecture, on Feb. 16, 

 1892,) I found it necessary to explain why the fleshy spiral arms of 



