542 L. F. S-patJi — A neiv Aonononite from Charviouth. 



should be mentioned, however, that here the periphery has also been 

 worn down, probably to the extent of several millimetres. It is to be 

 regretted that the state of preservation of this ammonite does not 

 permit of more exact comparison with the other specimens described 

 in this paper or with the genus Polyrnorphites. Tlie suture-line seems 

 to be considerably simpler than that of Dayiceras polymoiyhoides, 

 though it could not be exposed clearly enough for delineation. On 

 the other hand, the specimen shows the very peculiar costation of 

 D. polymorphoides in places (if less close), also, apparently, the 

 tyjDical peripheral ornament. In the circumstances it seems advisable 

 to consider it a distinct form from D. jwlymorjyhoides, and the name 

 Dayiceras langi ^ is here proposed. 



Since the development could not be studied in any of the specimens, 

 it may be premature to speculate on the probable evolution of the 

 new series and its connexion with the genus Polyrnorphites and the 

 other Polymorphidae. But in justification of the new generic name 

 proposed here the following observations may be offered. The 

 adult suture-line of Dayiceras polymorpJioides is of the complex tyjje 

 of certain finely-ribbed (and probably post-jainesoni) Uptonia, the 

 exact relationship of which both to typical UjJtonia and to Poly- 

 morp)hites has yet to be worked out.^ The t^qoical group of the 

 genus JJptonia has its maximum develojoment in the upper portion 

 of the jamesoni-zone, and the forms have a tendency towards 

 continuing the costation across the periphery. Without going, for 

 the present, into the complex interrelations of the family Poly- 

 morphidaB,^ it may be mentioned that some forms, indefinitely 

 referred to U. hronni (which, however, is keeled and has a com- 

 paratively simple suture-line), may show the lateral tubercles moved 

 considerably nearer to the siphonal line, also an indistinct notching 

 due to the median line of slightly raised apexes of the V's along the 

 periphery. So far as the writer is aware, however, nothing like the 

 fine and close costation of the new forms described here has been 

 observed in these Uptonia. The genus Polytnorpliites, on the other 

 hand, is characterized by a very simple suture-line. In the typical 

 forms of this genus (the small-sized, very variable Polymorphus 

 group, and not the forms of Gemmellaroceras, often included here) 

 tuberculation of the periphery also occurs occasionally, notably in 

 P. caprarius Quenstedt sp., though here the costse are bituberculate. 

 In the lineate species of the genus Polyrnorphites, however (with 

 merely angular periphery), there is a certain resemblance to the 

 new forms. But on present evidence it seems inadvisable to include 

 the new series which, at Charmouth, occurs in post-/6ea; times (yet 



1 Dedicated to Dr. W. D. Lang in recognition of his prolonged and pains- 

 taking investigations of the Liassic succession at Charmouth. 



- The writer considers that .-1. vernoscc Zittel, probably a Toarcian form, 

 does not belong to U%)tonia. 



^ Confined, in the writer's opinion, to the jamesoni and ihex zones, and not 

 including e.g. the Domerian Boukiceras and later Hildoceratids. 



