EXHIBIT AT PAN-AMERICAN EXPOSITION. 227 



SUTURE. 



Ceratites nodosus de Hann. 



TRIASSIC. 



< roettingen, ( Jermany. 1 163. 



A simple Ammonoid with the shell removed to show the suture line (colored red). 



DEVELOPMENT OF THE N A I II LOIDEA. 



i After Branco. ) 



Primordial chamber of Orthoceras from the Triassic of St. Cassian. Enlarged 18 

 diameters. 



DEVELOPMENT OF THE NAUTILOIDEA. 



( After Branco. I 



1. Primordial, second, and third chambers of Nautilus pompilius. Enlarged is 

 diameters. 



2. Section of same to show the beginning of the sipho. Enlarged 25 diameters. 



DEVELOPMENT OF THE AMMONOLDEA. 



(After Branco.) 



1. Primordial chamber of a goniatite (Mimoceras compressus) , enlarged 60 diame- 

 ters. 

 1?. Primordial chamber and first volution of same, enlarged 60 diameters. 



DEVELOPMENT OF THE A.MMONOIDEA. 



(After Branco.) 



1. Primordial chamber of a latisellate Ammonoid (Arcesles cymbiformis) , greatly 

 enlarged. The term latisellate lias reference to the suture (colored red) forming a 

 decided broad saddle on the venter. 



2. First volution of a latisellate Ammonoid. 



DEVELOPMENT OF THE AMMONOIDEA. 



(After Branco. ) 



1. Primordial chamber of an angustisellate Ammonoid (of the type of Phylloceras 

 heterophyllum.) enlarged 60 diameters. 



2. Section through the primordial, second, and third chambers, to show the 

 beginning of the sipho of an angustisellate Ammonoid. Enlarged !<•<• diameters. 



DEVELOPMENT OF THE AMMONOIDEA. 



I After Branco.) 



1. Primordial chamber of an angustisellate Ammonoid (of the type of Cosloceras 

 crassus), enlarged 60 diameters. The term angustisellate has reference to the sutures 

 (colored red) having prominent ventral saddles, with corresponding deep lateral lobes, 

 and definite saddles at the umbilical depression. 

 _. 3. First and second volution of an angustisellate Ammonoid. 

 4. First three volutions, showing the introduction..!' sutural inflections and shell 

 sculpture. 



DEVELOPMENT OF THE AMMONOIDEA. 

 i After Branco. | 



Section through the first and second volution of a latisellate Ammonoid | Tropites). 

 It shows the beginning of the sipho in the ceecal condition in the primordial chain- 



