1920.] Note on the cretaceous echinoid. 299 
Agassiz described two species under this generic name,' but 
the characters of the species differed, to such an extent, from 
those which were attributed to the genus, that d’Orbigny had 
to create a new genus (Botriopygus) for the reception of these 
i * but the 
this genus.2 This list was modified by Desor* and there 
have been subsequent additions to the list since then.’ In 
1898 Lambert created a new genus, Plagiopygus, to include 
the so-called (soi-disant) tertiary species of Pygorynchus,® but 
separate genus has been made out.’ 
According to Desor Pygorhynchus has a ‘ periprocte supra- 
marginal et transversal’ with ‘ peristome excentrique,’ while 
the figures and descriptions of the species I have been able to 
lay my hands on all agree in these two characters.’ Cassidulus, 
of which Pygorhynchus is a sub-genus, according to Duncan, 
has a peristome excentric in front. Thus it is clear that if 
figures and the few specimens collected by me. From an 
examination of these it is quite clear that the periproct is 
supra-marginal and longitudinal, while the peristome 1s central * 
and accordingly we may safely conclude that Cyrtoma and 
Pygorhynchus are not identical. ; 
Stigmtopygus galeatus, the type species on which Stigma- 
topygus, @’Orb., was established has a ‘ périprocte en forme de 
bouteille surmonté d’un bourrelet assez notable.’ © S. elatus 
has an anal opening quite different from this. In his synopsis 
| Agassiz: Echinodermes fossiles de la Suisse, Vol. I, pp. 53-57 
(1839). 
2 Pal. Fr. terr-cret., Vol. VI, pp. 334-342. 
3 Op. cit., p. 321. 
4 Desor: Synopsis des Echinides fossiles, p. S07. 
5eg. P. Tripolitanus, Krumm (Palaeontographica. LIII, p. 89 
6). 
6 Bull. Pal Tome XI M, p. 162. 
Bull. Soc. belge de Geol. et de Pa a es Coe. 
tert. Ist pt., pp. 25-28. There seems to be some confusion regarding the 
type of Pygorhynchus. It is usual to look upon P. obovatus as Agassiz’s 
: M’clelland: op. cit., p. 
2 
® Desor: op. cit., p. 288. 
