Association of American Geologists and Naturalists. 109 



An interesting oral discussion on the points brought under re- 

 view by Mr. Silhman's paper, was conducted by Profs. H. D. 

 and W. B. Rogers, Dr. Smith, of South Carolina, and Prof 

 O. P. Hubbard, of Dartmouth, which was not reported. 



After the recess at 12 o'clock, the business committee reported 

 the order of proceedings for the ensuing day. 



Mr. James Hall then read an abstract of a paper upon the 

 Brachiopoda and Orthocerata. 



The object was to show the variation in size and form among many 

 species of the Brachiopoda, depending upon the age and the condition 

 of the ocean bed upon which they lived. Mr. H. remarked that, when 

 a student in geology, and making pedestrian excursions with his asso- 

 ciates, the motto upon their knapsacks was, " nullum saxum sine nomi- 

 num est.'''' At that time there were, however, many rocks without names 

 to them. Since that time he had learned from experience that some 

 rocks had as many as five or six names. This remark was applicable 

 to a species of Atrypa, which occurs in great abundance in Ohio, Ken- 

 tucky and Indiana ; this had been received under different names in its 

 different stages, from the plain plicated form of the young specimens to 

 the expanded older form, to which Mr. Conrad has affixed the name of 

 A. capax. 



The same fossil, in its younger or smaller form, occurs in New York, 

 where it is known by another name. 



Similar observations were made in relation to a species of Delthyris, 

 which, under its different phases, has no less than six names applied to 

 it. The gradations in all cases he satisfactorily traced, leaving no doubt 

 of the propriety of referring the whole to a single species. The same 

 was true of other species of Brachiopoda, which would be exhibited to 

 the Association at some future time. 



The remarks upon the Orthocerata regarded a peculiarity in the 

 structure, which shows the existence of a long conical or terete tube, like 

 a Belemnite, within the siphuncle. In some specimens there was an in- 

 sertion of a second tube within the first, and in one case as many as five 

 concentric hollow tubes of this kind. This discovery was regarded as 

 new, and throwing additional light upon the structure of these remains. 



Some species did not exhibit this structure, and it may serve as the 

 foundation of a generic distinction. 



Specimens were exhibited showing the excentric siphuncle, and 

 these bodies, separately, were often regarded as distinct and indepen- 

 dent fossils. 



Mr. Lea called the attention of the meeting to the importance 

 of Prof. Hall's observations on the fossil Brachiopoda, where he 



