186 
to Mc. Murrich (1. c. p. 20) the scattered craspedonemes are pre¬ 
sent only on the macrocnemes in fimbriatus, in plicatus they are 
present also in the microcnemes (B and b) in form of bunches 
and in the macrocnemes scattered over almost the whole surface 
except ' the terminal part, where they are collected in bunches. 
Also the filament of the pg-mesenteries in does not seem 
to agree perfectly with those in plicatus. 
In the tubes of this species some specimens of a large Phoronis 
were found, very similar to the Phoronis australis Hasw. (Cf. p. 173). 
Genus Isarachnanthus n. gen. 
Di agn osis: Arachnanthidae (Acontiferidae), whose second 
couple of protomesenteries (ps) are long, sterile (always?) and pro- 
vided with acontoids. Metamesenteries of the first and second cycle 
(M, m) as p 2 without cnidoglandular tract but with acontoids on 
the best developed. Arrangement of the metamesenteries MBmb 
more or less distinet. Number of mesenteries comparatively few. 
Broad siphonoglyph and long hyposulcus. Without craspedonemes 
and bunches of the ciliated tract. 
While the p 2 -mesenteries in the genus Årachnanthus are short 
and devoid of acontoids (I here use this more indifferent name, 
proposed by Pax, instead of muco-craspedonemes), they are long 
and provided with acontoids in Isarachnanthus. Also the arrange¬ 
ment of the tentacles seems to be different in the two genera. In 
the till now examined species of Årachnanthus the marginal as well 
as the labial tentacles are arranged in a single cycle (the labial 
tentacles in Årachnanthus bockii possibly in two), the arrangement 
of the tentacles in Isarachnanthus agrees more with that in other 
Ceriantharia. The genus Årachnanthus is devoid of a directive labial 
tentacle, Isarachnanthus is furnished with one. Meanwhile, I have 
not included this character in the genus diagnosis, because till now 
only few species are known of these genera. 
Among the Ceriantharia provided with acontoids on p^-mesent- 
eries, two larval species are described by Mc. Murrich, the one, 
obconica, is placed by him in the larval genus Åpiaetis, the other, 
pilula, in the larval genus Peponactis. As we shall probably never 
be able to decide to which ripe Ceriantharia the larvae belong, it 
