46 
so long as we do not know whether this is a constant feature in 
the species, or whether the same condition is found in the young 
specimens (which is scarcely probable x ). 
Agassiz (Panamic Deep Sea Echini, p. 39) has pointed out 
the marked difference between the suranal plate of the Echinina 
and that of the Salenids, the former being inside the anal area, 
while in the Salenids it „never becomes part of the anal system 
proper 44 . In spite of this difference he evidently still regards these 
plates as homologous, as it is expressed in „Calamocrinus 44 (p. 79): 
„we are undoubtedly justified in considering the single anal plate 
of the young of such Echini as Strongylocentrotus .... as homo¬ 
logous with the single large anal plate of the Salenidæ 44 . This 
homology has, however, been disputed by Lambert (Note sur un 
nouveau genre d’Échinide de la Craie de l’Yonne. 1888, p. 9. 
Note). „Ce que l’on doit avant tout considérer, c’est la forme du 
bord interne dans les plaques normales solides de l’apex (genitales 
et ocellaires). Les bords de ces plaques sont-ils arrondis, de 
maniére a former le cadre irréguliérement circulaire d’un espace 
central, je djs qu’alors il n’y a pas de veritables suranales .... 
Mais les ocellaires et les genitales circonscrivent-elles un espace 
central å bords irréguliers avec angles plus ou moins saillants et 
rentrants, il est evident qu’elles ne formaient pas seules le cadre 
du périprocte et qu’elles devaient admettre des plaques complémen- 
taires plus ou moins persistantes, s’intercalant dans ces angles et 
constitutives de l’apex. Il y a entre ces plaques apicales et les 
plaquettes anales .... une difference fondamentale .... Les 
premieres sont constitutives du disque central; les autres, malgré 
une dérivation originelle, purement adventices, appartiennent plutot 
au périprocte 44 . I am not aware that Lambert has later on 
corrected this view. But the apical system of Palæopedina and 
x ) De Meijere (Siboga-Echinoidea, p. 78) states that the young Pleur- 
echinus bothryoides has only a single anal plate. The young spe¬ 
cimens, on which this statement is founded, are, however, not PI. 
bothryoides , but some other species of the genus Pleurechinus. (Op. 
cit. p. 202. Siam-Echinoidea. I, p. 81, 84). 
