50 COXOLAMPAS SIGSBEI. 
De Loriol has proposed the name of Phylloclypeus.* These discoveries 
led me to make a renewed examination of Conoch/jms Sigsbei. On opening 
a specimen I found that it was edentate, as liad been suggested by De 
Loriol from the presence of the well-developed phyllodes (PI. XVII. Fig. 5) 
characteristic of Echinolampas and of the edentate Conoclypus tjpe he 
called Phylloclypeus. On comparing the structure of the actinostome in 
Conoclypus Sufshci, as seen from the interior, with tliat of Echinolampas, I 
found very striking differences. As is well known, in Echinolampas Hellei 
(PI. XV. Fig. 9, Rev. Echini) the test immediately round the actinal open- 
ing rises slightly, in a conical shape, above the general level of the actinal 
floor. This is also the case in E. depressa, but in both cases the edges of 
this conical elevation form a smooth ring round the actinostome, the cone 
being in fact merely the turning up of the outer edges of the last plates 
immediately adjoining the actinostome. In Conoch/pus Sif/shei, on the con- 
trary, the structure of the ring of plates round the actinostome is quite 
similar to that described by Zittel and De Loriol in Conoclypus with 
teeth ; the processes which support the jaws, although wanting (PI. XVII. 
Fig. 4), are still indicated by slight angular knobs, and we also find the 
deep pits described by these authors in the interambulacral areas at the 
base of this elevated ring. 
This structural feature is one of the most interesting found among Echini, 
as it seems to show us the direct passage, as it were, between the edentate 
Echini and those provided with teeth. We have no full description as yet 
of the jaws of Conoclypus, but enough is known to show us how closely 
allied they are to those of the Clypeastroids. In Conoclypus they are evi- 
dently held in place by vertical processes, very similar to those which thus 
far have been considered as characteristic of the Clypeastroids. With the 
diminution in size of the jaws in these types we must expect to find genera 
in which the supporting processes alone are left, and we liiay look for them 
in the foi-ms allied to the genus Phylloclypeus of De Loriol. The next stage 
will be the practical disappearance of these processes, their former presence 
being indicated l)y mere knobs, as in Conoch/pus Sigsbei, until we get the 
typical modern Echinolampas, in which the plates forming the actinal ring 
rise only as a low cone above the general level of the actinal floor, and all 
traces of these processes and of the interambulacral actinal pits have dis- 
appeared. It m.ay be convenient for the present to call this modern rep- 
* M6m. de la Soc. Ue Phys. et cl'Hist. Nat. de Geneve, 1880, XXVII. 79. 
