320 MELLITA SEXFORIS. 



Mellita sexforis 



Eckinodiscus sexiesperforatus Leskk, 177s. Klein, Add. 

 I Mellita » eforis A. Agass. 1872. Rev. Ech. I't. I. 



PL XL f. 1-12; PL XP.f. 3. 



Five ambulacra! hmules and one posterior interambulacral one. The apex 

 and the mouth are central, or nearly so, while in the pentaphorous species 

 of Mellita they are quite eccentric. The ambulacral lunules are of the same 

 size, narrow, elongate, while the odd posterior lunule is usually somewhat 

 smaller than the others. The test in all the specimens examined slopes regu- 

 larly from the apex towards the edge. The outline is more or less circular 

 or pentagonal, but slightly truncated posteriorly. The ambulacral petals are 

 all ot* the same size, comparatively small, not reaching hall-way to the edge 

 of test from the apex. The median ambulacral space, included between 

 the poriferous zones, is as broad as each zone ; genital openings distant from 

 apex. The coronal plates of upper part ol test are all more or less convex. 



The ambulacral furrows ramify more at the extremity near the edge of the 

 test, on each side of the lunules. than in tin' other species, leaving hut a very 

 narrow median interambulacral space not covered by furrows. The large 

 tubercles of the lower surface are consequently fewer in number; they are. 

 at the same time, more uniform in size where they occur; the rest of the 

 lower surface of the test is covered by line granulation of smaller tubercles 

 near the poriferous furrows. The difference in size between the spines of 



the two surfaces is slight, their arrangement is the same, there are but few 

 comparatively large spines immediately round the mouth, the whole lower 

 surface being covered by silk-like spines not clavate. like those of the upper 

 part of the test. The color when alive is slightly yellowish, ranging through 

 all the shades of a dirty yellow to a light olive-green. The bathynietrical 

 range of this species is quite extensive (littoral-270 fathoms), though the 

 geographical range, as far as we know it. is not great, being confined to 

 the West Indies and to the Bermudas. 



Young specimens of Mellita sexforis, measuring 2.4 mm in diameter (PL 

 XL f. /). are almost circular, with a thickened raised edge as in Laganum, 

 and as yet have no lunules visible from the abactinal side. The rosette 

 is simply a series of radiating pores, three and two in each poriferous 

 zone, for each ambulacrum, extending but a short distance from the 

 apex, having the simple structure of the poriferous zone of non-conjugated 

 pores of Echinocyamus. The ambulacral and interambulacral plates are 



