EEPOET ON THE CEINOIDEA. 311 



The following key shows the mutual relations of the species described in this 

 Report : — 



A. No post-distichal axillaries. 



First radials visible ; arm-joints relatively long, . . . . 1. elongata, n. sp. 



First radials concealed ; arm-joints short and wide, . . . .2. simplex, n. sp. 



B. Three palmars, the axillary a syzygy. 



No post-palmars ; ten cirri of ten or twelve joints, . . , .3. rotalaria, Lam., bd. 



Post-palmars like palmars ; fifteen cirri of fifteen joints, . . . i. ralida, n. sp. 



1. Actinometra elongata, n. sp. (PI. LVII. figs. 2-4). 



Specific formula — a. 2 



Description of an Individual. — Centro-dorsal a small thin disk, bearing about ten 

 cirri of twelve or fourteen joints, a few of which are longer than wide. Three radials 

 visible ; the second partly united laterally, the remainder of the rays being well separated. 

 Two distichals, the axillary without a syzygy. 



Eighteen arms, which are all tentaculiferous, but dimorphic. The anterior arms taper 

 slowly, reaching 11 cm. in length, and consist of one hundred and twenty quadrate 

 segments, the middle and later ones of which are very long. The posterior arms reach 

 only 4'5 cm., and taper rapidly, with about fifty-five shorter but still quadrate joints. 



A syzygy in the third brachial ; the next between the sixth and tenth, with others at 

 intervals of about three joints. 



The pinnules diminish in length from the first one on the second brachial, which 

 reaches 8 mm., to those of the fifth and sixth, and then increase again, becoming very 

 long and slender at the ends of the arms. The first six or eight have a slight terminal 

 comb, which occurs at intervals to far out on the arm. The later pinnules of the 

 posterior arms have " ovoid bodies " on their dorsal edge. 



Mouth nearly radial ; disk naked. 



Colour in spirit, — -greenish grey. 



Disk 11 mm.; spread nearly 20 cm. 



Locality. — Banda ; October 1, 1874. 



Remarks. — This is a singular type in many ways. It differs altogether from the 

 majority of species of Actinometra in the great length of its arm-joints, which is 

 especially evident in the longer anterior arms (PL LVII. fig. 2) ; though the joints of the 

 posterior arms are also relatively long. The only form which comes at all near it in this 

 respect is the tridistichate Actinometra quadrata (PI. LXII. fig. 1). The great difference 

 in length between the anterior and posterior arms is the more remarkable, as they are all 

 tentaculiferous, none of them being unprovided with an ambulacral groove, as is so often 



