Anatomical Nomenclature of Echinoderms . 13 
which lodged the extensor ligament (muscle?). The plates 
of attachment for the flexor muscles between the first and 
second radials are in a more vertical position than the rest of 
the articular face, and when the second radials are in position 
five clefts are visible on the floor of the calyx, which were 
occupied during life by the five pairs of muscular bundles. 
These clefts are particularly well shown in Zittel’s own figure 
of the interior of the cup of Apiocrinus Parkinsoni *, while in 
de Loriol’s more recent figure of the same species j* they like- 
wise appear, together with precisely similar clefts between the 
radial axillary and the two brachials which it bears. The 
existence of a muscular articulation is admitted in the latter 
case, and it will scarcely be any longer denied that there is a 
similar articulation between the first and second radial. It is 
a peculiar one no doubt, owing to the great size of the dorsal 
fossa in some species of Apiocrinus. But this is well deve- 
loped in some species of Millericrinus , e. g. M. ranvillensis , 
and a regular gradational series may be traced from the most 
Pentacrinus - like forms of Millericrinus through M. ranvillensis 
to Apiocrinus elegans , and thence to forms like A. Meriani 
and others with large dorsal fossse. 
Even in these last there are distinct indications of a mus- 
cular articulation, while whenever the distal faces of the 
second radials or the proximal faces of the axillaries are 
visible they present a vertical articular ridge for a bifascial 
articulation, exactly as in Antedon rosacea and in most 
Comatulce \ . We find therefore that in the calyx of Apio- 
crinus there are two articular facets below that on the axil- 
lary radial, which is the first one admitted by Zittel ; and if 
Schultze's nomenclature be followed, Apiocrinus must be 
described as having but one radial, like Encrinus and Penta- 
crinus . The same will be the case with every other Neo- 
crinoid except Guettardicrinus , a genus which, as defined by 
d’Orbigny, is not admitted by Zittel; but de Loriol has 
pointed out that in this type there are no articular facets on 
either of the three radials, nor even on the distal faces of the 
second joints after the axillary §; and, in fact, it has not yet 
been determined what plate of the body of this type does bear 
the first facet. 
If, then, Schultze’s nomenclature is to be extended to the 
Neocrinoids, Guettardicrinus is the only type which can be 
said to have more than one radial. 
Steinmann and Doderlein || admit that the arms sensu stricto 
* Op. cit. p. 389, fig. 277 b. f Op. cit. pi. xxx. figs. 1 «, 1 b. 
t De Loriol, op. cit. pi. xxx. fig. 2 b y pi. xxxiii. fig. 2 a , pi. lvi. figs. 2, 2 c. 
§ Op. cit. p. 219. 
|| ‘ Elemente der Palaontologie/ Leipzig, 1888, p. 153. 
