198 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



ventral keel. Hyatt (1889) says Cymhites is probably only 

 the young of Agassizceras, while Haug considers the char- 

 acters upon which Neumayr based the genus not to be suf- 

 ficiently constant to warrant the separation, although he 

 regards the problematic species as adult forms. However 

 this may be, we know that the young of the more special- 

 ized Polymorphidas are like Cynibites, and whether the 

 forms described by Neumayr were adults or not, there 

 must have been such a genus as ancestor of the group, 

 and not only of this small section, but also of the yEgocer- 

 atidas as well; so it will be well to retain Cymhites, although 

 Buckman leaves this genus out of the Polymorphidee, 

 which he does not consider the primitive family. 



Another form that may possibly be in the genetic series 

 of the ^goceratidse, and thus of Placenticeras, is the genus 

 Diafhorites Fucini (1896, a and b, p. 232, PL XXV, figs. 

 i_i^), which, although small, is surely made up of adult 

 forms. This genus greatly resembles Cynibites, and is 

 thought by Fucini to be genetically connected with the 

 PhylloceratidiE ; the youthful stages of Diaphorites vetulo- 

 niits Fucini, as described and figured by that author, are 

 remarkably like the young of Placenticeras -pacijicum, sp. 

 nov., figs. 13 and 14 of Fucini's paper, reproducing exactly 

 the glyphioceran stage, and fig. 12 is like the Nannites stage 

 of Placenticeras. The early adult septa of Diafhorites, 

 copied on plate XXVHI, fig. 7, after Fucini, are almost 

 exactly like the early adolescent septa of Placenticeras, 

 and the parallel is also quite exact as to form and sculpture. 

 As only one species of the genus is known as yet, and that 

 only in Italy, it would be premature to single this out as 

 the connecting link between the perisphinctoid group, and 

 the phylloceran stock; the most we can say is that this con- 

 necting link must have been some such genus. 



Fucini (1896, a p. 124, and b p. 236, PL XXV, figs. i6~ 

 21) has described another genus, Pimelites, that might 

 possibly be the radicle of the eegoceran stock; it is very 

 like Diaphorites, differing only in some unimportant charac- 

 ters, and being, in Fucini's opinion, intimately related to the 



