324 ECHINODERMA OF THE INDIAN MUSEUM, FAKT VII. 



In one of them the distal ends of the segments of the lower pinnules are all 

 produced and finely spinous, in addition to the ])roduction of the distal 

 corners. 



OLIGOMETRA SERRIPINNA var. ERINACEA, var. nov. 



Description. — Centrodorsal as in typical 0. serrijnnna, thin-discoidal, tlie 

 dorsal pole flat, usually with a slightly raised rim, 2 mm. in diameter. 



Cirri XV— XVII, 21-24 (usually 23), 10 mm. to 12 mm. long; the oirri are 

 a trifle more slender than those of typical 0. ser r'i pinna , and usually have a 

 slight, though peiceptible, distal taper after the proximal half; the segments 

 are all short, most of them about half again as broad as long, not becoming as 

 long as broad until the second or third before the penultimate ; the dorsal 

 processes resemble those of the cirri of typical 0. serripinna , but the transverse 

 ridge toward the middle of the cirri shows a more or less marked division into 

 two halves, accompanied with a more or less deep and angular notch in the 

 crest, and in the outer part resolves itself into two laterally elongate tubercles 

 placed side by side. 



The structure of the arms and of the arm bases is in general as in O. serripinna : 

 the synarthrial tubercles on the joints between the elements of the IBr series and 

 between the first two brachials are enormously developed as in Perometra diomedece 

 or in Amphimetra ensifer, but their apices, though they may be smooth as in those 

 species, are usually blunted and spread out laterally, bifurcated, or armed with 

 several blunt spines : eacli (proximal and distal) half of the synarthrial tubercle 

 may be at the tip armed wit!i a sharp tubercle, the two tubercles pointing away 

 from each other at a considerable angle, or the proximal half of the synarthrial 

 tubercle may be distally laterally spread out and fan-like or dentate, and the distal 

 half almost or quite unmodified. The synarthrial tubercle between the first two 

 brachials as a rule departs more widely from the normal than that between the 

 ossicles of the IBr series. The IBr axillary has a usually very long and pronunent 

 tubercle on eitlier side of the anterior apex. 



The second and following brachials have the distal edge everted, standing 

 out at right angles to the dorsal surface as a very high finely spinous crest : on 

 the earlier segments this crest is laterally narrow so that it appears as a 

 high tubercle which maj- be slightly broadened or chisel-shaped at the tip, or 

 may be bifurcate or coarsely dentate; after the first syzygy this process gradually 

 broadens laterally so that after the second syzygy it comes to involve the 

 whole distal bender of the bracliials, which stand out as very high more or 

 less irregularly scalloped or dentate finely spinous vertical frills. The earlier 

 narrow projections are usually divided up into a few large tubercles, but the 

 broad later ridges are more uniform and more regular. 



The pinnules in general resemble those of typical O. serripinna, but tliey 

 are very much more ornate. P^ is 5 mm. long, very slender, with fourteen 

 segments of which the outer are considerably elongated and the outer five or six 



