ORIGIN AN1> CHARACTERISTICS OF SUBORDERS. 



The depressed serai-lunar whorl appears first in the adults of Anarcestes. It 



sequently found in the young as n stage immediately succeeding the more 



cylindrical whorl of the gyroceran Btage, when thai occurs. In very close-coiled 



forms, the latter may !><• omitted, <>r be only slightly indicated, and then the 



-n. in whorl appears at the beginning of the apex. In fact, this tendency 



sellati, and especially in Angustisellati, affects the Bhape of the protoconcfa 



which vely depressed in the embryos of the higher suboi 



have, ti considered it convenient rnate the anarces- 



tian form of whorl a< the primary radical of the Ammonoidea, reserving the 

 terms primitive and transitional radicals for the Btraight and gyroceran modi- 

 fications a* they appear in Bactrites and Mirao 



The diffi the Clymeninsa and Goniatitinse, and the Arcestinae, 



i with, and maintain persistently in full-grown Bhells, the primary 



: il form. Tin.- CeratitinaB, Lytoceratinse, and Ammonitinse, <m the contrary, 



have this depressed form buf rarely, except in their protoconchial stage, — 



ami at the beginning «>f the apes or true conch, while it remains in what we 



called the goniatitic stage of development 



Clymeninaa of the Devonian begin, when zoologically arranged, with 



i.il forms having depressed Beroi-lunar anarcestian whorls. These de- 



1 whorls are exchanged in the higher form- for compressed discoidal 



whorls, and these iu turn for compressed involute whorls. The suborder 



includ< genera and in each there occur examples <>t" this mode of 



or rather pn ssion, oi forms, forming parallel series. 1 



The sutures <>f the genera Beneckia, Longobard I. mites, Nbrites, 



- II inga rites, and Carnites show them to l" 1 true Ceratitinsa. We 



should, with our present information, !)<• disposed t<> include these, and all 



i mentioned by Bfojsisovica as belonging to bis group of 



: i, in the Ceratitinre, distinguishing them by their well-known and 



from the Arcestinae, Ammonitinse, and Goniatitinse. 



Ii npressed whorl, which in section imh be described as 



helmet-nhaped, is the natural successor of the depressed anarcestian whorl both 

 in the growth <>f individuals and in the evolution of series of species. We bave 

 considered this in the work quoted, therefore, as the secondary radical. 



The secondary radicals 1 are prevalent in the Ceratitinoe, as shown by the 



m the remarkable and masterly ti 

 I impletely replace the primary radicals as generators 



in th<- Trias, except in the pal the sub 



ncerned, however, the Ceratitinse, 



'■i distinctly ch of the triassic faunsB, are like th>- Goniatitinse. 



I l i- reallj 1 1 itite, similar to Prol< anitea 



i 



