1921 KOSMOCERATIDM 53 



Family KOSMOCERATIDM, Hyatt 



Ornati, Kuncinati, Auctt. Cosmoceratid;e, Hyatt (Ceph. ; Zittcl- 

 Eastman Pal. I, 1900, 587 — Kostnoceras is Waagcns' original spelling : 

 nomenclatorial rules forbid alteration of generic and trivial names ; 

 but a family name must agree with that of the genus). Hyatt placed 

 in Kosmoceratida;, Cosmoceras representing the Ornati, and created 

 Sigaloceras for the Runcinati. He also united with them his genus 

 Phricodoceras, but this is far removed in date : in that respect and in 

 suture-line it associates with Liparoceratida; (see T.A., II, p. b and III, 

 PI. CXLIX). 



Mostly scrpenticones and platyconcs (ex coronate cadiconcs ?) with 

 a specialized venter (see later) and liberally tuberculate on lateral, and 

 latero-peripheral areas — the most developed forms carrying two rows 

 of tubercles on each of these areas, that is, six rows on the conch. Often 

 with very long lateral prolongations to mouth-border. Transition in one 

 direction to rounded venter and forms with Macrocephalites aspect ; 

 in another direction to almost inornate, amblygastric oxycones, and 

 possibly in another direction to uncoiled forms : the so-called 

 Ancylocerates of the Callovian have the ornaments of the Ornati, and 

 are possible developments of Ornati scrpenticones. Suture-line not 

 elaborate, retraction and reclination of umbilical lobes feeble. 



Date of existence : Bathian ? Callovian, Divesian ; maximum in 

 Callovian : some of their strata preserved over wide areas in Europe. 



The venter, which may be called the Kosmoceratid venter, presents 

 itself in various styles : — 



(1) Runcinate-ornate : a median tabulate area, crossed by straight 



costa: or subcosta:, bordered by prominences, from swellings 

 to long spines. 



(2) Ornate : median band more or less smooth to quite smooth, 



tabulate to sunken, bordered by spines, alternate, opposite 

 or intermittent. The spines being septate, and the speci- 

 mens being usually found as pyritized casts, the length of 

 the spines may fail to be appreciated. 



(3) Runcinate : median band tabulate, crossed by straight costa;, 



which have no prominences at the angle of junction with 



lateral area. (Runcinate stage — Neumayr & Uhlig, 



Kaukasus Jurafoss. ;-Denkschr. Math. Nat. CI. K. Akad. 



Wiss. LIX, 1892, 54). 



There are many forms of venter included in the above headings. 



Some of them are due to change during developments ; but others arise 



from the differential development of characters in distinct lineages. 



The Kosmoceratid venter is one feature distinguishing Kosmo- 

 ceratida: from Parkinsonidae. The runcinate-ornate and the runcinate 

 stages, with ribs running straight and strong across venter, are not found 

 in the Parkinsonidae : in the true Parkinsonian venter, when ribs arc 

 on the median band, they are alternate and curve forwards to fade 

 away in the mid-line. The ornate venter, however, is comparable with 

 that in Strenoceras, Garantiana etc. ; but is not to be directly connected, 

 as it is not a primitive feature in Kosmoceratidpe : it is, presumably, a 

 modification of certain phases of the runcinate-ornate — therefore, it is 

 of independent origin from that of Strenoceras etc. Proof of this is also 

 found in the associated suture-line : it is more elaborate than that of 

 Strenoceras and allies. 



