146 PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



MEMORIAL OF ORV1LLE A. DERBY 



Dr. John M. Clarke then spoke of the loss to the Society by the death 

 of Dr. Orville A. Derby, Chief of the Geological Survey of Brazil, and 

 gave a personal appreciation of his character and life work resulting 

 from his long acquaintance with Doctor Derby and from their mutual 

 interest in Devonian paleontology. The memorial to Doctor Derby by 

 Professor Branner is published as pages 15-21 of this number. 



ANNOUNCEMENTS 



It was then announced that the Council had voted favorably on the 

 request of the Treasurer to transfer $300 of the Society's funds from the 

 Second National Bank of New Haven to the Connecticut Savings Bank 

 of the same place in order that this sum should bear interest. 



No further business remaining, the Society proceeded in general ses- 

 sion to the reading of the papers on general paleontology. 



PRESENTATION OF GENERAL PAPERS 



The first paper of the session was presented by the author and illus- 

 trated by lantern slides and specimens; 10 minutes. 



PRESENCE OF A MEDIAN EYE IN TRILOBITES 

 BY KUDOLPH EUEDEMANN 



(Abstract) 



The median or parietal eye which is present in lower crustaceans and also 

 in the phyllopods with which the trilohites are usually compared is. in the 

 majority of the Ordovicic and Siluric trilohites. recognizable in a tubercle on 

 the glabella. This tubercle has long been known to exist in all asaphids on 

 otherwise wholly smooth carapaces (see Schmidt, Revision der ostbaltischen 

 silurischen Trilohites) and is well known in Cryptolithus (Trinueleus) and 

 others; its regular occurrence is recorded in the literature of more than thirty 

 genera. It has been found by us to possess two distinct lenses, similar to the 

 median eye of the eurypterids, in Ptyclwpyge rimulosa; in others, as in Crypto- 

 lithus, but one lens; and in most cases it is simply a transparent spot of the 

 crust, often thinner, sometimes thickened lenslike, more or less elevated, corre- 

 sponding in these features to the prevailing character of the median eye in the 

 other crustaceans. Even as simple tubercle its visual function and nature of 

 a median eye is proven by its position between the lateral eyes, as in the other 

 arthropods — that is, nearest to the brain ganglia — and invariably on the high- 

 est spot of the glabella, which is the most favorable position for its visual 

 function. The eye tubercle is. as a rule, relatively largest in the earlier growth 

 stages; in some species, as Isotelus gigas, it disappears entirely with maturity. 

 In some Siluric and most Devonic genera, especially the Phacopida, the median 

 eye has, corresponding to the strong development of the lateral eyes, been more 



