Association of American Geologists and Naturalists. 109 



An interesting oral discussion on the points brought under re- 



r Mr. Silliman's paper, was conducted by Profs. H. D. 



W. B. Rog 



?rs, Dr. Smith, of South Carolina, and Prof 

 0. 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- 

 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 

 oiHerent 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. 



num 



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

 *tare it is known by another name. 



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



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



■ ihe gradations in all cases he satisfactorily traced, leaving no doubt 



e P^priety of referring the whole to a single species. The same 



^as true of other species of Brachiopoda, which would be exhibited to 



the Ass ociation at some future time. 



ihe remarks upon the Orthocerata regarded a peculiarity in the 

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

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

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



COncentnc hollow tubes of this kind. This discovery was regarded 



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



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



Ration of a generic distinction. 



pecimens were exhibited showing the excentric siphuncle, and 



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

 dent fossils. * i 



Mr 



portance 



rof ' Hall's observations on the fossil Brachiopoda, where he 



