348 THE VOYAGE OF H.M.S. CHALLENGED. 



Mouth interraclial or nearly so ; disk naked. or slightly plated. 

 Colour in spirit, — deep brown, the pinnules tipped with yellow-green. 

 Disk 27 mm.; spread 22 cm. 

 Locality. — Banda ; 17 fathoms. Two specimens. 



Remarks. — These two individuals seem to be different from that which I found in 

 the Leyden Museum and described under the name Actinometra schlegelii. 1 They show 

 much more of the first radials,. which are almost entirely concealed in the Lej^den species, 

 and have relatively longer arm-joints. This character is best marked in the middle and 

 outer parts of the arms, those of Actinometra schlegelii being much wider than long ; 

 while in Actinometra regalis the joints are more equally quadrate, and the overlap of the 

 lower joints is more marked. In this species too the pinnules of the fourth to sixth 

 brachials are quite small, which is not the case in Actinometra schlegelii. The number of 

 cirrus-joints in the latter type is not known ; but Actinometra regalis has less than 

 twenty, being thus distinguished from Actinometra peroni with its very long cirri of 

 thirty joints ; while in Actinometra bennetti there are fifty cirri of twenty-five joints. 



Genus 6. Promachocrinus, P. H. Carpenter, 1879. 



1879. Promachocrinus, P. H. Carpenter, Proo. Boy. Soc, 1879, vol. xxviii. p. 385. 



1880. Promachocrinus, P. H. Carpenter, Journ. Linn. Soc. Lond. (Zool.), 1880, vol. xv. p. 214. 



Definition. — Centro-dorsal hemispherical or conical, bearing numerous closely-set 

 cirri. Ten radials with high distal faces which have large muscle-plates. Mouth central; 

 ambulacra symmetrically distributed and not provided with any definite skeleton. 

 Sacculi well developed. 



Remarks. — The principal distinctive character of this remarkable genus, which is 

 only known from the dredgings of the Challenger, is the presence of ten radials in the 

 calyx instead of the usual five (PL I. figs. 1, a, b, c). In all other respects there are no 

 essential differences between Promachocrinus and Antedon. The species of the latter 

 genus to which Promachocrinus is most allied are those of the Eschrichti-gv oup, in 

 which the radials have high articular faces with large muscle-plates (PI. I. figs. 1, 6, 8, a). 

 The latter character also presents itself in Antedon accela, Antedon basicurva, and their 

 allies (PL II. figs. 1-5, a); but all these forms have a well-defined ambulacral skeleton 

 which is altogether absent in Promachocrinus. 



One of the three species of this genus was obtained at a depth of 500 fathoms off the 

 Meangis Islands (Station 214). Unfortunately, however, it is only represented by one 

 individual in a most mutilated condition (PL LXIX.' figs. 9, 10). But each of the other 

 two species occurred at two localities in the southern sea. The type-species, Promacho- 



1 Notes from the Leyden Museum, 1881, vol. iii. p. 210. 



